The question which presents itself almost on the threshold of every industrial enterprise, is that of the amount and cost of the fuel necessary to be consumed in executing the work: for in the existing condition of the Arts, it may almost universally be considered, that, directly or indirectly, the changes which are to be produced, whether in composition or in form, in the raw materials of any manufacture, are effected by the operation of heat. If we look to any of the various chemical or metallurgic arts, we find the agency of heat necessary to give liquidity to the substances employed, so that they may be run into moulds, or separated from infusible components; to effect their perfect mixture, or to bring into play those chemical affinities, by which their constitution may be altered, and new and more valuable products formed. Hence it is impossible
p.2to carry on those branches of industry in localities destitute of fuel, and where this is scarce and high priced, the cost of production of the manufactured article may be so augmented, as to absorb all profit, and render the prosecution of that trade only a source of loss. In a similar manner, although not in the same degree, the mechanical arts are influenced by the cost of fuel. In localities where water power is not available, it is necessary to employ steam. To produce any given motion, to spin a certain weight of cotton, or weave any quantity of linen, there is required steam; to produce the steam, fuel; and thus the price of fuel regulates effectively the cost of mechanical power. Abundance and cheapness of fuel are hence main ingredients in industrial success. It is for this reason that in England the active manufacturing districts mark, almost with geological accuracy, the limits of the coal fields. It is, therefore, easily conceivable, that in attempting to describe the materials which exist for the prosecution of industry in Ireland, the first step must consist in such an account of the sources of fuel at our disposal, as may determine its practical value, its distribution, its nature, its probable cost, and, as far as possible, its abundance.
The materials which we employ as fuel for our domestic and industrial purposes, are all derived from the vegetable kingdom, being either wood of modern growth, or else turf or coal, which are themselves but masses of vegetable matter of ancient growth, compressed and decomposed until they present their well-known aspect. In this country we may practically exclude wood from our consideration as a fuel; there is no feature of an Irish landscape more characteristic than the desert baldness of our hills, which, robbed of those sylvan honours that elsewhere diversify a rural prospect, present to every eye a type of the desolation which has overspread the land. This barrenness of trees is but of recent origin. Numerous localities, in every part of Ireland, derive their names from having been originally embowered in forests. In every district where man's neglect, combined with nature's rank luxuriance of vegetation, has given occasion to the formation of those bogs, for which our country has become a by-word,
p.3it is found that immersed in the turf are quantities of large timber, generally fir, birch, and oak; the former so impregnated with resinous material, that a splinter burns like a candle, and is employed as such. This resin is partly the native turpentine of the tree, but, for the most part, consists of peculiar bodies produced by the decomposition to which the wood is subjected, and by which, if the action were continued for a sufficient length of time, true bituminous coal should be produced.
That the country was some centuries ago remarkable for its extent of forests, as it is now by the reverse, appears from all our histories. Many causes conspired for their destruction. In some districts they were extirpated to increase the arable surface. In others in order to destroy the shelter which bands of outlaws found in their recesses. An extensive export trade in oak was at one time carried on, and two centuries ago the manufacture of iron was in great activity throughout this country, and led to the cutting down, as Boate says, of innumerable trees in order to prepare charcoal. During all this time, no one planted; all sought their immediate profit and cared not for the future, and the final result has been, that at present the timber grown in Ireland is not sufficient for those uses to which it specially is adapted, and as a fuel we may consider it never to be employed.
There is no doubt but that the coal has had its origin in the amassing together of great quantities of trees and plants, which constituted the vegetation of our globe at a period far antecedent to the appearance of man upon its surface. There is reason to suppose, that vegetable growth was then more active than it is now in the same localities. The plants whose forms may still be recognized in the beds of coal, belong, for the most part, not to the vegetation of the temperate climes, but to that which characterizes the scenery of the tropics. In the convulsions to which the superficial crust of the earth has been subjected, these forests have been destroyed; the growth of an immense surface, probably carried together by currents, has been engulphed and covered with mud and sand, and was thus subjected, under the influence of enormous pressure, and
p.4probably of an elevated temperature, to those decomposing agencies, by which vegetable matter, when in contact with moisture, is incessantly affected.
Under such circumstances, wood is converted into coal. The change is not sudden nor direct. It would be difficult to recognize in the masses of coal we usually burn, the forms of the plants from which it had its origin. But there are many varieties of coal. In the deposits of the true coal formation, the chemical changes have been carried on through such a lapse of ages, and under circumstances so favourable to their action, that it is now completed. But in geological epochs less remote, masses of vegetable remains have also been imbedded, in which we can study the intermediate states of change. It is thus by connecting the fossil wood or brown coal with recent wood upon the one hand, and with true coal upon the other, that we obtain an accurate view of the course of alteration which has produced this important fuel.
The alteration in the chemical composition of the wood, when it is converted into coal, is capable of being accurately traced and requires attentive study, as on it rest the comparative value of different kinds of coal as fuels. The composition of wood and of some of the most important of British coals, is given in the following table: supposing them free from ashes.
The alteration will hence be seen to consist in the removal of most of the oxygen and some of the hydrogen of the wood. These elements pass off combined with carbon, and are found haunting the recesses of the coal mine, under the forms of those damps or vapours so fatally known to miners, the oxygen and carbon forming the carbonic acid, termed choke damp, the
p.5hydrogen and carbon constituting the light carburetted hydrogen or fire damp. The quantity of carbon removed from the wood being comparatively small, this element preponderates the more in the residual coal as the decomposition has been more perfect, until finally in the anthracite or stone coal we find some specimens almost pure carbon.
When I bring before the reader the individual composition of the varieties of Irish coal, I shall again notice this table, and point out in what way the heating power of any kind of coal is connected with its composition. For the moment I shall lay it aside in order to notice somewhat further the geological relations of the various fuels.
The formation of coal in great masses appears to have occurred but in one geological period, though this may have extended over a great length of time, as we find the various portions of the coal formation to be separated from each other by strata of slaty rock or sandstone, of such thickness as must have required long years to form. Still the coal formation stands quite distinct from the formations that lie under and above it. In these there is no coal. In some localities of the most recent (tertiary) geological age, limited deposits of fossil wood are found, but they are unimportant, and we may consider coal as limited in its distribution to those rocks which lie between the mountain limestone on the one hand and the new red sandstone on the other.
It would not suit the objects of this work, to attempt a consecutive description of the geological structure of Ireland, or to enter upon the examination of its rocks and minerals in any general point of view, as it is only in reference to their industrial uses that they interest us, and the individual rocks can be best noticed in relation to the products which they furnish to the arts. On subsequent occasions, therefore, those rocky strata which are inferior in position to the limestone shall be noticed, as well as those more limited in their development in this country, which lie above the coal formation; but at present the structure of the districts in which fuel is to be found need alone occupy attention, briefly premising the description of the rock, the limestone, upon which our coal formation rests.
In this country the limestone formation is more developed than any other portion of the geological series. It is often called the mountain limestone, because in England where it was first examined, it rises into hills of considerable elevation, as in Derbyshire. With us that title cannot be applied. Its extent may be inferred from the fact, that from Dublin to the Bay of Galway, a direct line of 120 miles, drawn east and west, it touches no other rock, and from north to south, although its boundaries are irregular, its mean breadth may be considered at 100. Over this immense area, the surface is almost entirely flat; its average elevation over the sea not exceeding 300 feet, and, although undulating in its surface, the elevations which it forms seldom rise more than two or three hundred feet above the general level. This peculiar feature of our country brings with it many disadvantages and some advantages, to each of which I shall advert in the proper place.
The great scale of the limestone formation in this country has allowed of its being recognized, to be not one homogeneous rock, as it had been formerly described, but to consist of three formations, essentially different in character, and even in some degree as to the animal remains which they contain. Of these divisions the lowest is by far the most widely extended. It prevails most in the midland and southern counties, and furnishes us with some of the marbles of Galway and Kilkenny, Carlow, Mayo, and other places, which shall be again noticed. The neighbourhood of Dublin is occupied by the middle limestone, to which the name of calp was given by our celebrated countryman, Richard Kirwan. It extends rather towards the northern counties of Leinster, as Westmeath and Longford. It occurs also in Galway. It is much less pure than either of the other divisions of the limestone strata, containing often layers of soft shales, of impure coaly matter, of earthy ironstone, and of flinty slate. The uses to which it is most applicable shall be hereafter stated and its chemical composition shown.
The upper limestone occupies a smaller area, and is at once distinguished from the others by the physical character of the country which it forms. This is steep and rugged, presenting crags and precipices, with numerous caverns. To the localities
p.7of this rock belong the peculiar interest, that on it the coal formation rests. We hence find it encompassing those districts in which coal is found, or in which it may be expected to be discovered. To specially describe its distribution is, therefore, needless, as in examining the limits of our local deposits, I shall in fact, point out the localities where it is found. It is only useful to remark, that its greatest development is on the southern and eastern coasts of Galway Bay, where, rising from under the great coal formation of the Munster district, it constitutes the rugged mountains of Burren, and forms much of the country between Galway and Sligo, the hilly character of which distinguishes it so remarkably from the greater flatness of surface of the calp, and of the lower limestone counties of the centre and south.
Interposed between the limestone and the true carboniferous beds, there exists a great sandstone deposit, which, from one of the most important uses of its materials, is known as the millstone grit. The relations of this rock are so identified with the coal measures, that the notices of localities are the same for both, and need not be separated.
The coal formation of Ireland consists of a series of sandstone and slaty rocks, which rest upon the upper limestone, and give an aspect of considerable elevation to the districts. They are seven in number; of these one is in Leinster, two are in Munster, three in Ulster, and one in Connaught. These districts differ materially in their produce, according as they are situate to the north or to the south of Dublin. Those to the north yield bituminous or flaming coal: those to the south yield only stone coal or anthracite, which burns without flame. There is no doubt but that this difference results from the geological circumstances of those portions of the island, but it would not suit our purpose to enter into that question.
We will commence the history of our coal districts with that of Leinster.
This deposit occupies the greater portion of the county of Kilkenny, of the Queen's County and part of Carlow. It is bounded on the east, west, and south, by two great rivers, the Barrow and the Nore, which run immediately at the base
p.8of the Colliery Hills. Its general appearance, when viewed from a distance, is that of a very steep ridge of high land running in a direct line for many miles, rising from 800 to 1000 feet above its base, and apparently flat on the summit. It presents this character on every side, but when viewed from the eminence itself it resembles a great barren table land rising precipitously above a flat and highly cultivated country.
This district constitutes a great mineral basin; its strata consequently incline from the edge towards the centre, the undermost appear on the outer edge, and the uppermost in the interior of the district. The strata consist of beds of slate clay, containing abundant thin veins and nodules of ironstone, compact sandstone, and sandstone slate; with these are interposed beds of fire clay, and the coal beds, of which there are altogether eight workable, arranged in regular succession. These strata require to be more specifically described.
Slate clay is usually the most abundant rock of the coal formation. It is a dull earthy mineral, which easily divides into thin flakes. It decomposes rapidly when exposed to air; its colour varies from black to grey; it is sometimes very hard or even flinty, which especially occurs where it comes into contact with the subjacent limestone. The quantity of ironstone associated with this rock is very large, its composition and uses will be hereafter noticed.
The sandstone of the coal formation consists of silicious sand cemented by a paste of lime or clay. It contains numerous vegetable impressions. This sandstone frequently becomes micaceous and slaty, so as to split easily into layers, producing the well-known Carlow flags.
The roof of the coal beds is sometimes sandstone, and sometimes slate clay. The floor of the bed is generally a clay, locally termed coal seat. This substance is soft and earthy; I shall hereafter describe its composition, at present I need only mention that it is equal to the best Stourbridge clay, for all the purposes for which that substance is employed.
The beds of coal in the Leinster district are, as already stated, eight in number, distinguished by the following names, arranged in the order of their position from below upwards;
The seventh and eighth beds, being those lying next the surface and easiest worked, have been exhausted; the sixth bed, or first three foot coal, which for the last century has principally supplied the wants of the surrounding country, is now considered by Mr. Griffith as nearly worked out. The inferior beds have been but little, some not at all touched, and must be the theatre of future mining operations. Of these the most important is the four foot coal, and its description will serve as an example of the rest.
The upper part of this bed is composed of five feet five inches of slaty coal (locally termed kelves), under which are three feet of hard coal, containing some sulphur pyrites, then a bed of black slate clay of six inches thick, and lastly one foot of coal containing a thin bed of kelve near the bottom, making altogether a height of coal, kelve, and slate of ten feet, of which but four feet are solid coal. Mr. Griffith estimates the area occupied by this coal at 5000 acres (Irish), and as its specific gravity is 1.591, the total quantity of pure solid coal may be calculated at rather more than sixty-three millions of tons. On the average this bed appears to lie about eighty yards below the first three feet bed of coal, and at a depth of from 100 to 140 yards from the surface.
Formerly the extraction of the coal was very badly managed. The imperfect methods of drainage obliged many shafts to be abandoned when they arrived at a certain depth, a large quantity of coal was left behind, and the amount of labour was excessive. Hence coal was high-priced, 20s. a ton for coal, and from five to eight shillings for small coal or culm. But since Mr. Griffith's report, and especially by the exertions of the late Mr. Aher, much progress has been made in introducing a better
p.10system. The use of the steam engine for draining has enabled shafts to be reworked that had been totally abandoned. The quantity of coal raised is estimated at 120,000 tons per annum, and it is sold at a price of about 11s. 6d. per ton for coal, and four shillings per ton for culm.
The chemical and economic qualities of this coal will be described, when I have noted the geographical circumstances of the remaining anthracite basins.
The Tipperary coal field is indeed a portion of that already noticed, being separated from the Kilkenny coal field by a narrow intervening neck of limestone. It extends about twenty miles in length from Freshford to near Cashel. It is about six miles broad in its widest part; the towns of Killenaule and of New Birmingham mark its centre. It forms a range of hills from 300 to 600 feet in height, abrupt on the north-western, but sloping on the south-eastern side into the limestone plain. The general nature and arrangement of the strata is the same as has been above described, but they dip at a steeper angle and undulate. Hence the coal lies in deep troughs, from which arises a peculiar mode of working, the shaft being sunk in the centre of the trough, and the coal wrought by working upwards on both sides of it.
This district appears to contain but three beds of coal. The lowest but nine inches, the others are each two feet thick. The quantity of coal at present raised has been estimated at 50,000 tons per annum. The price at which it is at present sold may be estimated at 12s. per ton for good coal, and 4s. per ton for culm.
Proceeding further to the south and west we arrive finally at what is peculiarly termed the Munster coal field. This tract, the most extensive development of the coal strata in the British Empire, occupies considerable portions of the counties of Clare, Limerick, Cork, and Kerry. In all four counties coal has been discovered, and coal mines worked. The physical features of the country are similar to those described in the Tipperary district. The coal consequently lies in a series of troughs, the hills striking usually from east to west, and the strata (lipping on either side, north and south, at considerable
p.11angles, often perpendicular. From this peculiarity of structure, the estimate of the precise condition of the coal becomes difficult. The same beds frequently reappear in different parts of the country, thrown up by contortions of the strata to the surface, and might then, on superficial observation, be counted as distinct deposits. From Mr. Griffith's investigations it appears, however, that there are six distinct layers of coal. Of these, three of the most valuable, locally known as the bulk-vein, the rock-vein, and the sweet-vein, have been recognized on the opposite sides of three of the undulations. The detailed examination of this district has not, however, been as yet carried on to a sufficient extent to enable us to trace the entire arrangement of the strata.
The most extensive collieries at present worked in this district are situate in the barony of Duhallow in the county of Cork. The beds of culm present themselves in numerous places over the west coast of Clare, and along the estuary of the Shannon. The beds, although thus of enormous superficial extent, are unfortunately not thick; the coal is softer and more slaty than in the Tipperary and Kilkenny districts. This applies, however only to the thinner beds; the veins mentioned above in Duhallow, and which are from two to three feet in thickness, produce an excellent anthracite, of which some analyses shall be hereafter given.
Such are the beds of non-flaming coal or anthracite which occur in Ireland. We shall pass to the description of the coal of the northern portions of the country, which is bituminous coal.
A small but highly-interesting coal field occurs in Tyrone. The country round it resembles a great geological museum, containing rocks of every epoch from the granite rising from beneath all, to those tertiary clays which constitute the latest term of the geological series, and of which, in relation to the stores of fuel they contain, I shall soon have occasion to speak. The limestone of Dungannon may be considered as forming the base of the Tyrone coal district. It is covered by strata of sandstone, limestone, and slate clay, with clay-ironstone, fire-clay, and coal. The external character of the country
p.12is similar to that of the southern coal field. It is an assemblage of low hills, with steep acclivities and flattened summits. Here, however, when the hills exceed a couple of hundred feet in height, they are capped with new red sandstone or trap, or even with both. This district is geographically subdivided into the Coal-island and the Anahone basins; but as the latter is a very unimportant outlier, I shall only describe the former.
The Tyrone coal burns rapidly with flame, and evolves great heat. Its composition and economic power will be hereafter noticed. The sandstone and slate are generally analogous to those rocks in other coal fields, and need not be further noticed. The ironstone and fire-clay will be specially described further on.
The linear dimensions of the Coal-island field are six miles by two; its area about 7000 acres. The Anahone district contains only 320 acres yet recognized, but it may extend under the new red sandstone through a much larger area.
Notwithstanding the smallness of this basin, its strata are so much contorted and disturbed, as to cause great irregularity in the workings by changes of level, and the occasional disappearance of the bed of coal from amongst the broken strata. Slips and shifts of the layers of rock also occur, though not more frequently than in other coal fields. But notwithstanding these drawbacks, this basin merits special attention. The coal is excellent; it is not difficult to raise, and its quantity is such as to be capable of diffusing the blessings of industrial prosperity over an extensive area.
From Mr. Griffith's report, it appears that there are in this basin six workable beds of coal. The names of these beds, and their usual thickness, are as follows:
|Bed of Coal||Thickness|
|Ft. In. Ft In.|
|1. Annagher coal||8 0 to 10 0|
|2. Yard coal||2 0 to 3 0|
|3. Brackaveel coal||4 9 to 5 0|
|4. Balteboy coal||0 9 to 3 0|
|5. Derry coal||4 6 to 5 0|
|6. Gortnaskea coal||2 0 to 6 0|
|Total||22 0 to 32 0|
From 22 to 32 feet of solid workable coal is thus found within a depth of 120 fathoms, and it is remarked by Mr. Griffith that amongst the numberless pits of the English coal fields, there is no example of the same thickness of coal within the same distance from the surface. The collieries in this district are worked, some by the Hibernian Mining Company, and some by private companies of persons belonging to the neighbourhood. The industry of the latter has been and is profitable. The works of the former have hitherto been carried on at a loss. Whence comes this difference? The materials for answering this question may present themselves in a subsequent portion of this work.
At the northern extremity of Antrim is found a coal district, unimportant as to magnitude, but remarkable from its association with the great basaltic mass from which the characteristic scenery of Fairhead and the Causeway is derived. This coal field differs from all the others in this country in wanting the underlying limestone, and resting directly on mica slate. In this, certainly very rare, peculiarity, it is not, however, without parallel, the coal district of St. Etienne in France being similarly circumstanced. The face of the precipices to the sea, where sufficiently free from the debris of the basaltic rock, presents sections of this coal formation which fully illustrate its structure. At top the entire is covered by from 50 to 100 feet of the columnar greenstone, which spreads over the entire district. Under this are beds of reddish sandstone, slate, and coal. At Mulvagh Bay, the beds of coal are six in number, of which four are bituminous and two anthracitous. The latter are found, one immediately above, and the other close below a range of columnar basalt of seventy feet in thickness, which lies in amongst the coal strata. It might hence appear that these beds also had been originally bituminous, and that the basalt injected at an intense heat had distilled off their volatile portions, converting the residue into anthracite. There are, however, other and strong reasons against such an idea. Thus the beds of coal which lie close under the upper range of basalt are fully bituminous, and the effects of heat shewn where trap dykes traverse the bituminous beds, and convert them into true coke,
p.14is quite different from anything visible in the lower beds which consist of a real anthracite.
The quantity of coal which remains in this district is so small, that further detail concerning it is unnecessary. It appears to have been the oldest worked colliery in Ireland, perhaps in the Empire, as during the year 1770 the miners broke into an old gallery, the walls of which were lined with stalactites, evidently of great age, and antique mining tools were found therein. The residents in the district had never heard of a tradition of the mine having been anciently worked, and the excavation must have been made at a very remote period indeed.
The bituminous beds of coal are each about two feet six inches thick. The upper bed of anthracite is also of the same thickness. This latter appears, however, to be impure and sulphurous.
In Monaghan a small coal basin rests on a patch of the carboniferous limestone which is insulated within the slate district. The strata dip at so large an angle, as to render the working very difficult, and as no beds exceeding twelve to fourteen inches in thickness have been found, this coal district need not be considered as of any value.
We arrive now at the last of the coal fields of this country. The Connaught district. It is one worthy of attention from its peculiar geographical position, and from the circumstances connected with the attempts made to establish the manufacture of iron within its bounds. Those attempts, with the history of the too notorious Arigna Company, shall be treated of hereafter. The localities of the coal only occupy us now.
The largest river in the British Islands falls into the Atlantic Ocean, dividing the counties of Clare and Kerry, and cutting through the centre of the Munster coal formation. Expanding in its inland course into a chain of extensive lakes, it intersects through a line of 247 miles, some of the richest lands in Ireland, washing the banks often of the thirty-two counties of which our island is made up. It has its origin in the recesses of the Leitrim hills, where it springs almost with its full power from a vast gulf, the depth of which has not
p.15been yet ascertained, and almost immediately expanding forms Lough Allen, of which the area is 8900 acres. The picture of this district, as I saw it some two years since, has never left my mind. The dark brown hills, heather clad, rose abruptly from the water, excepting towards the south, where they were separated from the lake by level spaces of marshy bog. The patches of cultivation, small and rare, far from relieving the aspect of the scene, served but to render its dreariness more oppressive. The lake, smooth as a mirror, reflected the brilliant sky of midsummer. No wave disturbed it; the noise and bustle of active industry were far away. The melancholy solitude of my walk was only broken by the approach of some wretched men, who had heard of the phenomenon of a stranger's presence in their wilds, and pressed around, asking whether I was about to do anything for the country, to give employment. Alas! it was not in my power. As I walked on, there lay around my path masses of iron ore, equally rich with the best employed in England. I knew that in those hills, whose desolate aspect weighed on my mind, there were concealed all the materials for successful industry. A population starving, and eager to be employed at any price. A district capable of setting them at work, if its resources were directed by honesty and common sense. But all sacrificed to the stock-jobbing speculations of a few men acting on the gross ignorance and credulity of some others. If the industrial circumstances of this country were really known, such events as the jobbing of the Arigna Company could not have occurred. Let us hope that by the progress which science and education have since made, and are now making, the occurrence of aught similar may be for the future prevented.
The hills which surround Lough Allen form the Connaught coal field; they occupy large parts of the counties of Roscommon, Sligo, Leitrim, and a portion of Cavan in Ulster. The greatest length of the district is sixteen miles, which is also its greatest breath. The total area is about one hundred and fourteen thousand Irish acres. Seen from the south, they present a steep and straight ridge of from 1000 to 1200 feet in height. The summits flat and usually covered with bog. The
p.16centre of this district is occupied by Lough Allen. The circuit of the lake may be conveniently divided into four parts, with respect to its content in coal. The rocks are similar to those of the other coal fields. They consist of sandstone, sandstone slate, slate clay, clay ironstone, and fine fire clay. The strata are very regularly arranged, conformably to the limestone on which they rest, and contrary to the declivity of the hill. Slips occur as in all coal fields: they do not present anything peculiar here.
West of Lough Allen, the River Arigna divides the field into the southern and western portions. The former consists of one great mountain ridge named Brahlieve. At its base are the Arigna Iron Works. The western division extends between the Arigna and Dorobally rivers. These two portions have almost the same internal structure. Upon the limestone rests slate clay, in thickness from 300 to 600 feet. This rock is remarkable for the rich beds of ironstone which it contains. These are exposed in the channel of the River Arigna in incredible numbers. Then many beds of sandstone, and next, the fire clay, which as in the Leinster district, form the seat of the coal.
The beds of coal found in this district are three in number, and were first described with detail in Mr. Griffith's report on the Connaught coal formation. As the extent and characters of these beds of coal will be found of high importance, and that opinions differ regarding them, I shall transcribe, in full, the most important of Mr. Griffith's observations.
Of the first Bed of CoalThe fire clay is succeeded by a bed of coal, which varies in thickness from one to three feet. It is known in the country by the name of the crow coal. It contains numerous thin laminae of black slate clay, which render it of little value, except for burning lime. When first brought to the surface it is moderately solid, but on exposure to the air it soon divides into thin flakes.
This bed has never been wrought. If it were, I have little doubt its average thickness would be found to amount to three feet, but it has never been seen excepting at the outgoing. In the vale of the Arigna, near the iron works, where the fire clay
p.17was wrought, this coal was three feet thick. This coal runs parallel to the three foot coal which lies above it, and its outgoing may be traced along the face of the hills through the greater part of the southern and western division of the district.
p.18thickness. It is the uppermost bed of coal in the district, and has not been met with except in the southern division.
On the three foot coal several collieries are worked. Of these the Rover and the Aughabehy are the principal. The former are situated very near the iron works, the latter farther distant. Coal from the Santnavena and from the Meenashama pits will also be found amongst those of which the composition will be given farther on.
At the time that Mr. Griffith visited the locality and reported on it, the collieries were in such a wretched condition, flooded with water, their machinery out of repair, and the persons engaged about them so ignorant, that complete accuracy in the information he obtained could not be expected, and it would appear that the results above given require some alteration. The Arigna Iron Company commissioned Mr. Twigg of Chesterfield, a person practically conversant with collieries and iron works, to examine their holdings in this district, and he made several reports on the subject, of which a very excellent digest has appeared in the Survey of Roscommon, published by Mr. Weld.
From Mr. Twigg's reports, it would appear that the bed of coal as it sinks into the mountain, rather diminishes in thickness. He found it in the chisel pit at Aughabehy two feet seven inches thick. Mr. Weld found it in a pit which he examined to be less than two feet. Mr. Twigg estimated the working coal ground at Aughabehy at 160 English acres, and that at an average of 2550 tons per acre it should yield 408,000 tons of coal. The working area of the Rover colliery he valued at from 80 to 100 English acres. Mr. Twigg made no survey of the general area of coal in the district such as that made by Mr. Griffith (5000 Irish acres).
These coal beds being at a higher level than the general surface of the country, admit of being worked under the most favourable circumstances. The expense of raising the coal is very small; Mr. Griffith calculated that the cost of it at the pit's mouth was four shillings per ton, and when the iron works were in operation, it was contracted for at five shillings per ton.
p.19Several collieries have been worked in an imperfect and desultory manner. It is to be hoped that the future history of this locality may be different from that of the past.
The mountains, which form the northern portion of this district, do not present such favourable pictures as that last described. The thick beds of coal have not as yet been traced upon them, and indeed some features in their structure render it improbable that they exist; several thinner beds have, however, been found; and a further examination is desirable. The eastern portion of the district, separated from the last by the River Owenmore, consists of one mountain group, Slieve Neeran (the Iron Mountain). Its structure and stratification differ only in detail from that of the southern and western portions, and it contains also three beds of coal, of which the superficial extent is very great. The total thickness of the coal is less, however, and the strata are more broken. It has not been much worked. Indeed for a long time the southern and western divisions will fully suffice for all industrial wants.
Such are the circumstances of the coal field of Lough Allen. Although subsequent examination has sobered down the expectations of its produce which were once held, it must still be considered as capable of becoming an important centre of industry for the interior of this country. The causes which led to the failure of the iron manufacture at Arigna, might have acted as forcibly in Staffordshire or at Merthyr. Those causes may be removed. The quantity of coal available is certainly sufficiently great for domestic trade, and it must be recollected, that on the surface of the hills which surround Lough Allen there is a supply of fuel, probably not inferior to that which is contained within them. I have mentioned already that Mr. Griffith considers his original estimate of thirty millions of tons as too high. An estimate given in the Report of the Railway Commissioners in 1838, may probably be considered as embodying all accurate observations made. The Lough Allen district is there stated to contain 20,000 acres of coal, equal to twenty million tons. At present there is very little coal raised. The quantity does not exceed 3000 tons per annum.
Having described the geographical and geological conditions of the coal fields of Ireland, I shall now proceed to trace the composition of the coals they yield, and ascertain how far they are adapted for use. To represent their constitution I have given in every case the practical analysis, which shews the quantity of gas given off at a red heat, and that of the coke produced; the actual weight of coke being the sum of the ashes and of the pure coke. The heating power of each fuel was experimentally determined, and in most instances the elementary analysis has been executed.
This coal is described by Mr. Griffith as intermediate to the open-burning or quick-blazing coal of Scotland and the caking coal of Whitehaven. Mr. Twigg called it a coking coal of good quality. I have found it moderately bituminous, burning with flame, and leaving a white ash in moderate quantity. Its only disagreeable character was a great degree of friability.
I have submitted to accurate examination four kinds of it, transmitted to me through the kindness of Colonel Jones, Member of the Shannon Commission. I shall describe the results which I obtained.
A rich, black coal, easily broken. Its specific gravity 1.274. When heated it gives off a good deal of inflammable gas, and leaves a light, porous, grey, coherent coke. Analysed in this way it was found to give from 100 parts:
Its economic value as a fuel was determined by measuring the quantity of oxygen it was capable of absorbing on ignition with litharge. One part of it reduced twenty-six parts of lead to the metallic state; 100 parts of it, therefore, represent seventy-seven parts of pure carbon.
Those two coals are almost identical in external appearance. Their specific gravities about 1.290; when ignited, they give off inflammable gas, but do not froth; they produce a moderately dense coke, and leave, when burned away, white ashes. Their analysis was found to be, in 100 parts:
Ignited with litharge, one part of Santnavena coal gave twenty-six of lead, and one part of Meenashama coal twenty-five of lead. Hence, 100 parts of Santnavena coal corresponded to seventy-seven, and of Meenashama to seventy-three of pure carbon.
This coal is rather brown in aspect, and has a remarkable tendency to split into cubical fragments. Its specific gravity is 1.287. When ignited it gives out gas, but does not froth. Its coke is porous, slightly coherent. It contains less foreign matter than any of the other kinds. On analysis, its composition was found to be
One part of it gave, by ignition with litharge, 28.4 parts of lead, hence 100 parts of the coal correspond to 84 of pure carbon.
The prices of these coals, as given in a notice attached to the specimens, are
The Aughabehy and the Rover coal being the most important of this district, I thought it interesting, in addition to the more practical kind of analysis given above, to determine their actual elemental composition, which I found to be as follows:
It is thus seen, that the Aughabehy is a much more bituminous coal than the Rover, which approaches nearer in its character to the anthracites of the south. I do not know whether in the geological relations of the district there is anything capable of explaining the fact. The Santnavena and Meenashama coals have an intermediate quality.
This coal burns rapidly, and gives out intense heat. It cakes but little, and strongly resembles Ayrshire coal. My colleague, Mr. Davy, examined the Brackaveel coal from Coal Island, and the Kingarrow coal of Dungannon. The former had specific gravity of 1.266, and gave 65.9 per cent. of coke, containing 29.4. The latter had specific gravity 1.307, and gave 66.9 per cent. of coke, containing 37.0 of ashes. The following analyses by myself give the composition and properties of specimens of coal from the new Drumglass colliery, and from the pits of Messrs. Caulfield at Coal Island.
It is brilliant, black, friable, frequently mixed with the pyrites, which oxidize on exposure to the air; its ashes consequently usually reddish. On ignition it gives off much gas, froths, and gives a light porous coke. It was found to be composed of,
One part of it gave with litharge 22 parts of lead, hence 100 parts correspond to 65 parts of pure carbon.
This coal has a slaty structure, is dull coloured, but tolerably pure. Its specific gravity is 1.267; when ignited it gives off much gas, tumesces, and leaves a very porous coke. Its practical analysis gave,
It is, therefore, much purer than the Drumglass coal. One part of it gave, with litharge, 26.5 of lead; hence 100 parts correspond to 78 of pure carbon.
To illustrate further the composition of the coal of this basin, its ultimate constitution was determined,it was as follows:
I found the coal of Ballycastle dull, black in colour, its specific gravity 1.279. On ignition it gave out much gas, frothed very much, and left a porous coke. It consisted of,
One part of it gave 25 of lead; hence 100 parts of it correspond to 71.4 of pure carbon.
Of the economic relations of these coals nothing need be said. They are applicable to every use in industry, to which coal is applied in England. The remaining kind of coal, the anthracite
p.24of the South of Ireland, will require more consideration in that respect.
A remarkable feature in the coal fields of the South of Ireland is the large quantities of iron pyrites which are associated with the coal, and which evolving sulphurous fumes when burned, renders much of it totally unsuited for domestic use, and even for many purposes in the arts. The thicker beds are, however, free from this objection, and it is to the pure anthracite that I shall apply the following observations. The composition of anthracite is very uniform. From its not caking or burning with flame it is very generally termed mineral charcoal, and considered to be pure carbon mixed only with ashes. Hence its composition is generally expressed as in the following instances. Mr. Griffith, in his valuable report on the Leinster district, gives the composition of the
|First Bed of Slate Coal||per cent|
|Four Foot Coal||per cent|
The specific gravity of the four foot coal was found to be 1.591.
What is here termed carbon, is really the whole combustible and volatile material of the coal. This will appear from the following examination of the Irish anthracites which I made for the purposes of this work.
The specimens which I analysed were from
The Rushes coal, Queen's County, Leinster district.
The Pollough coal, Castlecomer, Leinster district.
The Sweet-vein, Kanturk, Munster district.
The anthracites have no tendency to froth or cake in coking. They give off little or no inflammable gas on being ignited, but usually the masses break up quite small, especially if the heat
p.25be suddenly applied. The ashes are almost always red, owing to oxide of iron remaining after the combustion of the pyrites, which the anthracite usually contains.
By the practical mode of analysis these coals yielded:
The results of ignition with litharge was, that one part of the
Rushes anthracite gave 31.8 of lead.
Pollough anthracite gave 26.7 of lead.
Sweet-vein anthracite gave 29.0 of lead.
Hence they correspond respectively,
100 parts of Rushes to 93.5 of pure carbon.
100 parts of Pollough to 73.5 of pure carbon.
100 parts of Sweet-vein to 85.3 of pure carbon.
I determined the elementary composition of these three varieties of anthracite, and found it to be as follows
Of these coals, the Sweet-vein was perfectly free from sulphur; the Rushes contained very little, but the Pollough a good deal. As this sensibly affects the determination of the carbon in the above analyses, I determined the exact quantity in this last coal, and found it to be 6.18 per cent., and hence the true composition of the Pollough coal was:
|Bisulphuret of iron||11.58|
|Ashes without iron||2.19|
The pure anthracite thus considered separate from ashes or sulphur consisted of,
Hence these coals, when pure, differ principally in the amount of hydrogen; the Sweet-vein containing most, and the Pollough least. The Rushes may be considered as representing the usual composition of this kind of coal.
The anthracite is thus shewn to be by no means mere mineral carbon; it contains a sensible quantity of hydrogen and a trace of oxygen. But these elements are not present in such proportion as admit of flame or smoke in burning, or the production of bituminous vapour or gas by distillation at a red heat.
This peculiar composition of anthracite affects its use as a fuel in the arts in an important degree, being the source of many advantages and of some defects, which, together with their remedies, it is necessary to describe. In consequence of its density and closeness of texture, anthracite is difficult to burn, except when in large masses, and conducts heat but slowly. For this reason also it is liable to splinter up into small fragments. These peculiarities are easily accommodated in practice. One much more important to consider arises from the fact that it contains very little volatile combustible material, but consists almost entirely of dense, solid carbon, and produces, in good draft, a most intense heat, which is, however, almost confined to the immediate neighbourhood of the fire. Thus, if anthracite be used as the fuel under a steam boiler, the heat in the fire-place may become so great, as to melt away the bars of the grate, and to burn out the bottom of the boiler, and yet the air passing into the flues may not be of such temperature as to produce an evaporation by any means economical. In such case we must call in the aid of science to free our fuel from this disadvantage. It is at once done by passing the vapour of water through the mass of red hot anthracite; the water is decomposed; its
p.27oxygen combines with carbon, and forms carbonic oxide; its hydrogen is set free. These mixed combustible gases pass into the flues, and inflaming in the excess of air which enters, give a sheet of flame which I have seen to extend for thirty feet under and through a boiler. The anthracite is thus converted into a flaming coal. There is no loss of heat; there is no gain of heat either, as some persons have supposed, but the action, beneficial in its result, is to absorb, in the first place, the excessive heat which was doing local injury, and to distribute it over the entire surface of the flues, where its maximum of good can be obtained. The principle of this method has been long known. Its application has been patented in England, but such patents can only stand for the particular mode of applying the watery vapour therein described, if even for so much.
Anthracite burning without smoke, and giving an intense though local heat, assimilates itself to coke, the most costly of our fuels, and hence it is interesting to inquire whether it can be used in what is now the principal employ of coke, in the fires of locomotive engines. On this point but little has as yet been experimentally ascertained. In England it is not of much importance; but one trial has been made which gives promise of its being perfectly successful in that use. I extract from the Mining Journal, quoting a report to the Directors of the Liverpool and Manchester Railway.
In the first instance the engine ran out with a load about six miles, and the coal was found to do very good duty, without any difficulty being experienced either with the tubes or the getting up of the fires. The engine brought back a load of coal waggons from the Heyton Colliery, and acquired, thus loaded, a speed of twenty-one miles an hour. Another trial was made in the evening with the same engine for the whole distance to Manchester, taking five loaded waggons. The journey was accomplished in an hour and twenty-five minutes. The consumption of anthracite was only 5½ cwt., although a large portion was wasted, from the fire bars being too wide apart for the economical use of this fuel. The engine would have used
p.28upwards of 7½ cwt. of coke for the same journey with the same load.
Should this result be confirmed by experiments continued for a longer time, it may exercise important influence on the railway economy of this country.
The heating power of anthracite is very great. I have found, and my results confirm those of Berthier, that it is capable of reducing to the metallic state, from 28 to 32 times its weight of lead. Pure carbon gives 35 parts of lead. The bituminous fuels give from 25 to 30. Now the economic value of a fuel, the quantity of water it can boil, or the quantity of iron it can melt, will be found proportional to these numbers, and hence, where the other conditions are rendered suitable for the employment of anthracite, it must be considered one of the best fuels.
Before entering on the history of our coal strata, I noticed some of the more ancient rocks on which they rest, and which I shall fully describe when examining the circumstances of our metallic veins. Above the coal formation, there are also extensive series of rocks, the new red sandstone, the oolite, the lias, and the chalk, which occupy in England large portions of the surface, but with us are developed only in the north-eastern corner of the island, forming the County Antrim and part of Derry, and overtopped by those masses of igneous rocks, the trap, and basalt, which chiefly characterize the locality. Some details of special industrial applications of these rocks may hereafter require notice, but I shall now pass from them in order to describe a very peculiar deposit of fuel, more recent than the coal; the Lignite of Lough Neagh. Encompassing the southern half of the lake from Washing Bay in Tyrone, to Sandy Bay in Antrim, this deposit consists of alternations of white, brown, and bluish clay, with white sand and beds of lignite or wood-coal; and, on the margin of the lough, of the silicified wood for which that lake is so celebrated. In some parts of this deposit the lignite is so abundant, that pits are sunk to raise it when other fuel is scarce. The vast quantity of lignite may be judged from a boring at Sandy Bay described by Mr. Griffith. In seventy-six feet of depth there occurred
p.29three beds of lignite, one of twenty, one of twenty-five, and one of fifteen feet thick, giving a total thickness of strata of fuel of sixty feet; the remaining sixteen feet were clay. Elsewhere the beds of lignite are not so much developed, but as the area of this tertiary basin extends over one hundred square miles, the quantity of fuel therein contained may be considered of much public interest. The clays of this basin are analogous to those of Bovey, where pipe-clay is obtained, along with lignite; whether good pipe-clay can be had in the basin of Lough Neagh has not as yet been tried.
The lignite has been already described as intermediate between wood and coal. This is shewn in its composition, given in the following analyses from this district.
The lignites examined retained all the structure of wood, and were of a deep brown colour. When ignited they gave off gaseous matter, which burned brilliantly, and left a dense black charcoal. In this way they were found constituted of,
By ignition with litharge, No. 1 gave 19.6 times its weight of lead, and No. 2 gave 16.7 times its weight. Hence,
100 parts of No. 1, correspond to 58 of pure carbon.
100 parts of No. 2, correspond to 50 of pure carbon.
Their elementary composition was found to be as follows :
|No. 1||No. 2|
The economic value of the lignite appears from these analyses about two-thirds that of average coal. The heat which it
p.30produces is more diffused than that from coal, and less intense. Indeed in all respects as to application to industrial uses, the position of lignite is between those of coal and wood.
The last of our sources of fuel that I shall proceed to describe, is of comparatively modern formation, and is considered most specially characteristic of this island; it is our turf. Our bogs may become, under the influence of an enlightened energy, sources of industry eminently productive. It is a fuel of excellent nature. We see it in ordinary use spoiled by its mode of preparation. It is here my duty to point out how it can be properly prepared, and economically used. Its importance to Ireland will, I trust, justify me in entering into some detail as to its nature, its composition, and its preparation. The excessive moisture of this climate, and the tendency to the growth of certain mosses, are the primary cause of bogs. The process of their formation is well described by Captain Portlock in the Memoir of the Ordnance Survey of Londonderry:
In the production of bog, sphagnum is allowed on all hands to have been a principal agent, and superabundant moisture the inducing cause. To account for such moisture, various opinions have been advanced, more especially that of the destruction of large forests, which, by obstructing in their fall the usual channels of drainage, were supposed to have caused an accumulation of water. That opinion, however, cannot be supported,for, as Mr. Aher remarks in the Bog Reports, such trees as are found have generally six or seven feet of compact peat under their roots, which are found standing as they grew, evidently proving the formation of peat to have been previous to the growth of the treesa fact, which, in relation to firs, may be verified in probably every bog in this parish, turf from three to five feet thick underlying the lowest layer of such trees. It is, indeed, so strongly marked in the bog, which on the Donegal side bounds the road to Muff, that the turf-cutters, having arrived at the last depth of turf, find timber no longer, though formerly it was abundant, as is proved by their own testimony from experience, and by the few scattered stumps which still remain resting on the present surface. Not so, however, with oaks, as their stumps are commonly found resting
p.31on the gravel at the base, or on the sides of the small hillocks of gravel and sand, which so often stud the surfaces of bogs, and have by Mr. Aher been aptly called islands. He further adds, that in the counties of Tipperary, Kilkenny, &c, they are popularly called derriesa name deserving attention, whether viewed as expressive of the existing fact, or as resulting from a lingering traditionary remembrance of their former condition, when, crowned with oaks, they were distinguishable from the dense forest of firs, skirting the marshy plains around them. The strong resemblance to ancient watercourses of the valleys and basins which now contain bog, and the occurrence of marl and shells at the bottoms of many, naturally suggest the idea of shallow lakesa view of the subject adopted in the Bog Reports, by Messrs. Nimmo and Griffith. Such lakes may have originated in the natural inequalities of the ground,or been formed by the choking-up of channels of drainage by heaps of clay and gravel,or they may have been reduced to the necessary state of shallowness by the gradual wearing-away of obstacles, which had dammed up and retained their waters at a higher level. Mr. Nimmo describes the mode in which the basin of a bog has been banked in by the alluvial deposits of a river (during freshets), and, in a similar manner, numerous examples might be adduced of bogs separated by banks of clay and gravel, owing to rivers running at their base, and below their level.
In some cases also clay, which is so frequently found spread over gravel at the bottom of bogs, has produced a kind of puddle, which, by retaining the waters of floods or springs, has facilitated the formation of muddy pools.
In all such cases the process may be thus stated:A shallow pool induced and favoured the vegetation of aquatic plants, which gradually crept in from the borders towards the deeper centre. Mud accumulated round their roots and stalks, and a spongy, semi-fluid mass was thus formed, well fitted for the growth of moss, which now, especially sphagnum, began to luxuriate. This, absorbing a large quantity of water, and continuing to shoot out new plants above, while the old were decaying, rotting, and compressing into a solid substance below,
p.32gradually replaced the water by a mass of vegetable matter. In this manner the marsh might be filled up, while the central, or moister portion, continuing to excite a more rapid growth of the moss, it would be gradually raised above the edges, until the whole surface had attained an elevation, sufficient to discharge the surface water by existing channels of drainage, and calculated by its slope to facilitate their passage, when a limit would be in some degree set to its further increase. Springs existing under the bog, or in its immediate vicinity, might indeed still favour its growth, though in a decreasing ratio; and hereif the water proceeding from them were so obstructed as to accumulate at its base, and to keep it in a rotten, fluid statethe surface of the bog might be ultimately so raised, and its continuity below so totally destroyed, as to cause it to flow over the retaining obstacle, and flood the adjacent country.
In mountain districts the progress of the phenomenon is similar. Pools, indeed, cannot in so many instances be formed, the steep slopes facilitating drainage,but the clouds and mists, resting on the summits and sides of mountains, amply supply their surface with moisture, which comes too in the most favourable form for vegetationnot in a sudden torrent, but unceasingly and gently, drop by drop. The extent of such bogs is also affected by the nature of the rock below them. On quartz they are shallow and small; on any rock yielding by its decomposition a clayey coating, they are considerablethe thickness of the bog, for example, on Knocklaid, in the county of Antrim, which is 1685 high, being near twelve feet. The summit bogs of high mountains are distinguishable from those of lower levels, by the total absence of large trees.
The total area of Ireland is twenty millions of acres. The total area of bog is estimated at 2,830,000 acres; nearly one-seventh of the entire surface of the island. Of these bogs there are 1,576,000 acres of flat bog; the remaining 1,254,000 acres are mountain bog. The former is spread over the central portions of the great limestone plain; the latter is principally distributed through the hilly country which ranges along the coast. In an industrial point of view, it is the central district
p.33of bogs which deserves attention. Some special circumstances which affect certain localities may require consideration in a different point of view; at present the subject must be considered under its general relations as to the constitution and application of this fuel.
As turf includes a mass of plants in different stages of decomposition, its aspect and constitution vary very much. Near the surface it is light coloured, spongy, and contains the vegetable remains but little altered. Deeper, it is brown, denser, and more decomposed; and finally, at the base of the greater bogs, some of which present a depth of forty feet, the mass of turf assumes the black colour, and nearly the density of coal, to which also it approximates very much in chemical composition. The amount of ash contained in turf is also variable, and appears to increase in proportion as we descend. Thus in the section of a bog forty feet deep at Timahoe, those portions near the surface contained 1½ per cent. of ashes; the central portions 3 1/4 per cent., whilst the lowest four feet of turf contained 19 per cent. of ashes. In the superficial layers it may also be remarked, that the composition is nearly the same as that of wood, the vegetable material being but little altered; and in the lower we find the change into coal nearly complete. Notwithstanding these extreme variations, we may yet establish the ordinary constitution of turf with certainty enough for practical use, and on the average specimens of turf selected from various localities, the following results have been obtained.
Turf, in Ireland, is usually sold by measure, not by weight, and as our results refer to weight, it is necessary, in comparing cost, to ascertain the density of average turf, as sold. The specific gravity of the light surface turf is about 400, water being 1000, and from this it increases, with the compactness of the structure, to nearly the density of coal. A cubic yard of good turf, packed close in sods, weighs about 900 lb. The densest turf well packed will go so far as 1100 lb per cubic yard; but the light turf, of which so much is burned, may not weigh more than 500 lb. The density of the turf, which these numbers illustrate, affect many of its technical
p.34uses, as shall be hereafter shewn. For comparison I may mention, that the cubic yard of solid coal weighs nearly a ton; but the coal in fragments as sold and burned weighs but 13 cwt. per cubic yard: it is, therefore, about twice as dense as average turf. Furnaces to burn the same weight of coal and turf would require double the capacity for the latter.
By means of the following analytical results, the general practical qualities and the chemical composition of turf may be considered to be established. The specimens were selected from Cappoge in Kildare, and Kilbeggan in Westmeath, on different sides of the great Bog of Allen, and from Kilbaha in Clare, where an extensive district of bog exists.
When ignited, the turf gives off inflammable gas, much water, and leaves a light, easily combustible charcoal. I found the specimens analyzed to yield,
|Light Turf||Light Turf||Dense Turf||Dense Turf|
By ignition with litharge it was found that:
One part of Cappoge turf gave 13.0 of lead.
One part of Kilbeggan turf gave 14.2 of lead.
One part of Kilbaha turf gave 13.8 of lead.
Hence 100 parts corresponded
Of Cappoge turf to 37 of pure carbon.
Of Kilbeggan turf to 41 of pure carbon.
Of Kilbaha turf to 40 of pure carbon.
I determined also the elementary composition of these turfs; the results were as follow:
Turf contains much less nitrogen than coal. Hence the liquor obtained in distilling turf contains no free ammonia. On the contrary it is acid from acetic acid, but even of this it yields so little that it cannot become, as occurs in the case of wood, an object of manufacture.
The calorific power of dry turf is about half that of coal. It yields, when ignited with litharge, about fourteen times its weight of lead. This power is, however, immensely diminished in ordinary use by the water which is allowed to remain in its texture, and of which the spongy character of its mass renders it very difficult to get rid. There is nothing in the industrial economy of this country which requires more alteration than the collection and preparation of our turf. Indeed I may say, that for practical purposes this valuable fuel is absolutely spoiled, as it is now prepared. It is cut in a wet season of the year; whilst drying it is exposed to the weather; it hence is in reality not dried at all. It is very usual to find the turf of commerce containing one-fourth of its weight of water; although it then feels dry to the hand: but let us examine how that affects its calorific power. One pound of pure, dry turf will evaporate six pounds of water; now in one pound of turf, as usually found, there are three quarters of a pound of dry turf, and one quarter of a pound of water. The three quarters of a pound can only evaporate four pounds and one-half of water. But out of this it must first evaporate the quarter of a pound contained in its mass, and hence the water boiled away by one pound of such turf is reduced to four pounds and a quarter. The loss is here 30 per cent.; a proportion which makes all the difference between a good fuel and one almost unfit for use. When turf is dried in the air, under cover, it still retains one-tenth of its weight of water, which reduces its calorific power 12per cent.; one pound of such turf evaporating five and one-third pounds of water. This effect is sufficient, however, for the great majority of objects. The further desiccation is too expensive and too troublesome to be used, except in some especial cases, of which the more important shall be hereafter noticed.
The characteristic fault of turf as a fuel is its want of density, which renders it difficult to concentrate within a limited
p.36space the quantity of heat necessary for many operations. The manner of heating of turf is, indeed, just the opposite to that of anthracite. The turf yields a vast body of volatile inflammable ingredients, which pass into the flues and chimney, and thus distribute the heat of combustion over a great space, whilst in no one point is the heat intense. Hence for all flaming fires, turf is applicable; and in its application to boilers it is peculiarly useful, as there is no liability to that burning away of the metal, which may arise from the local intensity of the heat of coke or coal. If it be required, it is quite possible, however, to obtain a very intense heat with turf, as I shall notice when speaking of the manufacture of iron.
I have already noticed the area over which turf may become available for industry. It comprises the central limestone plain, ramifying into Clare and Mayo. The cost at which turf may be consumed in the immediate neighbourhood of the bogs, I consider to be, from pretty numerous inquiries, not above 3s. 6d. per ton, but in our subsequent calculations I shall take 4s., in order that the error, if any, may be in excess of cost. I shall consider, however, that the turf is dried in the air under cover, which if our industry ever becomes active, and our fuel economized, must be the ordinary practice. Its economic value may then be practically assumed as 44 per cent. of that of ordinary coal. The turf at 4s. per ton costs as much to give a certain heat as coal at 9s. 1d.
The removal of the porosity and elasticity of turf, so that it might assume the solidity of coal, has been the object of many experimenters, who have proposed mechanical and other processes for the purpose. Amongst those we may mention Lord Willoughby D'Eresby, whose anxiety to improve the condition of the industrial classes deserves the highest praise. Lately with us Mr. Charles Wye Williams has brought into use various preparations of turf, and has given considerable impulse to the utilization of this kind of fuel. It has been found, that the elasticity of the turf fibre presents great obstacles to compression; and the black turf which is not fibrous, is of itself sufficiently dense. The only modes that present promise of successful issue, are those invented by Mr. Williams. One of
p.37these consists in drying the turf well, and then impregnating it with tar, which renders it waterproof, as it were, besides augmenting its calorific power. Turf so prepared has no tendency to re-absorb moisture, which is the serious failing of turf that has been perfectly dried, and the expense of thus bitumenizing the turf is, I understand, very trifling. It is said to be manufactured for from 6s. to 8s. per ton, and from the trials that have been made with it upon a very considerable scale, it appears to have a calorific power little inferior to coal.
All of those machines which have been invented for pressing turf, sod after sod, by manual labour, become ultimately too expensive to allow of their being profitably used. It is only by operating on a great scale, and with powerful machinery, in fact, only by manufacturing compressed peat largely for sale that the operation can be made to practically succeed. This is what Mr. Charles W. Williams has so well effected at Cappoge. The turf, when fresh cut, has its fibre broken up as far as possible, and is then placed between cloths, and pressed by a hydraulic press of great power. The condensation is to about one-third of the volume, and it loses about two-fifths of its weight, by the water, which is forced out in the pressing, and subsequently dried out. The sods of turf so prepared, even when formed of the very upper and spongiest stratum of the turf, are denser than wood. They have little or no tendency to grow damp, and it is found that including all labour, wear and tear, and original cost, this compressed peat can be delivered at the works for 5s. per ton. When this compressed peat is carbonized it gives a fine coherent coke, which contains very little ash, and amounts to about 30 per cent. of its weight, when the coking is properly carried on. The density of this coke is greater than that of wood charcoal, being found to range from 913 to 1040; the turf from which it was made having a specific gravity of from 910 to 1160. Its cost when manufactured does not exceed 20s. per ton.
The employment of turf as a source of heat in industry is extending; already it supplies exclusively the steam boats on the Shannon and a great number of distilleries and mills. From
p.38the numerical facts that have been given, the economy of its use may be inferred and compared with that of other fuels.
Not merely may we utilize turf in its natural condition, or compressed, or impregnated with pitchy matter, but we may carbonize it as we do wood, and prepare turf charcoal, the properties of which it is important to establish. The methods of carbonization are of two kinds. 1. By heating the turf in close vessels; by this mode loss is avoided, but it is expensive, and there is no compensation in the distilled liquors, which do not contain acetic acid in any quantity. The tar is also small in quantity, and the gases are deficient in illuminating power. Hence the charcoal is the only valuable product. Its quantity varies from thirty to forty per cent. by weight of the dry turf. The products of the distillation of 1154 lb of turf, were found by Blavier to be:
474 lb charcoal or 41.1 per cent.
226 lb watery liquor or 19.3 per cent.
7 lb tar or 6 per cent.
450 lb gaseous matter or 39 per cent.
1157 lb in total or100.0
The quantity of tar is very variable; thus the turf used in the iron furnaces at Voitoumra gives, when coked in close vessels.
The economical carbonization of turf is best carried on in heaps in the same manner as that of wood. The sods must be regularly arranged, and laid as close as possible: they are the better of being large, fifteen inches long by six broad and five deep. The heaps, built hemispherically, should be smaller in size than the heaps of wood usually are. In general 5000 or 6000 large sods may go to a heap, which will thus contain 1500 cubic feet. The mass must he allowed to heat more than
p.39is necessary for wood, and the process requires to be very carefully attended to, from the extreme combustibility of the charcoal. The quantity of charcoal obtained in this mode of carbonization is from 25 to 30 per cent. of the weight of the dry turf.
The charcoal so obtained is light and very inflammable. It possesses nearly the volume of the turf. It usually burns with a light flame, as the volatile matters are not totally expelled. This is shewn by the composition of a specimen analysed with the following result:
|Oxygen and nitrogen||4.20|
This charcoal is usually very light and friable. It is hence peculiarly fitted for the manufacture of gunpowder, and Mr. Derust, Pyrotechnist to Vauxhall, who experimented with it at the request of Mr. Williams, reported that it stood the several tests and was 20 per cent. more combustible than wood charcoal.
For many industrial uses, the charcoal so prepared is too light, as, generally speaking, it is only with fuels of considerable density that the most intense heat can be produced: but by cokeing compressed turf, it has been already shewn, that the resulting charcoal may attain a density of 1040, which is far superior to that of wood charcoal, and even equal to that of the best coke from coal. The importance of this result in the metallurgic relations of this fuel I shall hereafter notice. As to calorific effect, turf charcoal is about the same as coal cokes and little inferior to wood charcoal. This is shewn in the table, page 43, and it has been found to give from twenty-six to thirty parts of lead by its reducing action upon litharge. It is peculiarly important in the preparation of the charcoal from turf, that the material should be selected as free as possible from earthy impurities, for all such are concentrated in the coke, which maybe thereby rendered of
p.40little comparative value. This is remarkably shewn by observing the composition of the coke from the four varieties of turf, the analyses of which are given in p. 34. Thus the cokes consisted in 100 parts of
|Light Turf||Light Turf||Dense Turf||Dense Turf|
Hence the coke from surface turf contains not 10 per cent. of ash, whilst that from the dense turf of the lower strata contains from 20 to 30 per cent. This latter quantity might altogether unfit it for practical purposes.
Such is the description of our sources of fuel, so far as I have been able to collect facts regarding them. I have been anxious to remove exaggerated ideas of opposite characters which have been entertained. Although destitute of the grand development of mineral fuel which has rendered the sister kingdom the centre of the industrial arts, we yet possess several coal districts of considerable extent, and yielding large supplies of fuel, and moreover, there is in our bogs amassed a quantity of turf, which, if the peculiar characters of that fuel be suitable attended to, may become of eminent importance to the country.
All the applications of fuel depend, however, on its cost, and the amount and consequences of the cost of fuel in Ireland shall form the next subject of inquiry.