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rest or repose of the earth's crust, when a primeval forest reared its top above the waters until the vegetable matter now forming each bed of coal was grown and deposited. Then such forest was submerged and buried under mud and sand, now found as shale and sandstone rocks. The hollow caused by such subsidence is silted up until it is again covered over by shallow water. Then again a fresh crop of vegetation flourishes, so as to form another bed of coal. For 120 times does this successive growth of vegetable matter, submergence, and silting up go on. In some instances, whole forests of Sigillaria, standing upright in fine shale, on the top of the seams of coal, are met with, thus clearly showing that they were submerged quietly and slowly; whilst at other times the prostrate stems now found lying in sandstone, and other roots, show that the submergence was rapid, causing strong currents, that tore up and drifted the trees. All the floors of coal seams are full of the roots of Sigillaria (Stigmariæ); so with the stems of trees in the roof, vegetable matter in the seam of coal, and roots in the floor: there can scarcely exist a doubt, therefore, as to the remains of the vegetables now composing coal having grown on the spot where it is now found, and that stigmaria was the characteristic root of the plant, which for the most part produced coal.

The constituents of the gaseous mixtures given off by coals when compared with the known composition of wood and coal, enable us to form a very probable conjecture respecting the mode of their formation. It is now admitted that coal is the product of the gradual decomposition of wood, by » kind of mouldering process in the presence of water, pressure, and a limited supply of air. These agencies have all had a share in the transformation; but we are unable to trace the influence which each may have separately exerted towards the ultimate result.

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together.

We obtain the elements of splint coal

The whole of the coal fields of Great Britain are disjointed and fractured portions of one great field, and although the true foundation of our national greatness, and larger than any other yet discovered in Europe, are of small extent when compared with the enormous coal fields of the United States, which in extent probably exceed all those of Europe put

The exact areas of the different coal fields

, and how much coal they are likely to produce, it is difficult to state with any degree of precision, da no one yet can tell how far the seams of coal may be worked under their overlying deposits.

There has lately been published by Government in the report of the inspectors of coal mines, a summary of the production of coal during the last year (1857), with the number of lives lost. As it contains much information in a small compass, I shall give it entire. It is as follows:-"During the year 1857 there have been 74 explosions of fire damp, 360 accidents from falls of roof, coal, and sides of workings, 144 in shafts, miscellaneous 182, making a total of 760 accidents: of these there have been 377 lives lost by explosion, 372 by falls, 162 in shafts

, and 208 miscellaneous, making a total of 1,119 lives lost. During the year 1856 there were about 230,000 persons employed in and about the collieries of Great Britain, and about 667 million tons of coal Taised. The loss of life by accidents was, therefore, at the rate of about one person killed in each 224 employed, and one killed for each 64,751 tons of coal raised. In the year 1857 the production of coal was consider* Ronald's and Richardson's Chemical Technology, Vol. 1, PART 2, p. 514.

ably increased in some districts, whilst in others there was a slight decrease, the total production being probably 68 million tons. The loss of life therefore in 1857 is about one person killed for each 60,769 tons produced. This serious loss of life amongst persons following a peaceful occupation, is deserving the attention of the country at large, and imperatively demands the best efforts of the owners, agents, and workpeople. The Inspectors have, on the whole, to acknowledge the increased attention which has been paid towards improving the management since the passing of the present act; but it is obvious that in some districts accidents occur in consequence of defective management; and the Inspectors cannot too strongly recommend to the colliery owners and agents in such districts the employment of viewers, combining practical knowledge with scientific attainments. The efforts being made by the owners and managers of collieries, and others, in various parts of the country, to establish mining schools, are the result of the long acknowledged want of a special education, as applied to coal inining, and appear to the Inspectors to deserva encouragement." The number of men employed, and the vast amount of coal produced by the mines of Great Britain, is truly a source of national pride, and may be well adduced as a proof of the material power and wealth of the nation. But when we look at the loss of 1,119 valuable lives, we are obliged to confess that it has been purchased at an incalculable loss. Coal mining, no doubt, must always be an employment fraught with more or less danger, but still it is conceived that many of the above lives could have been saved by the exertions of officers possessed of the science, skill, and mining knowledge necessary for the command of a mine, aided by an intelligent body of sober, steady, intelligent, and well-disciplined working miners. All the above accidents are well worthy our attention; but on the

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present occasion we shall confine our attention to the consideration of explosions of fire damp.

Fire damp, sulphur, or wild fire, as it is commonly called by the colliers, is the light carburetted hydrogen or marsh gas, which is so commonly found bubbling up in our ponds of water, wherein is much decomposing vegetable matter. This gas is often seen in

on the surface of water, and is sometimes fired by boys for the purpose of amusement. It conaists of one equivalent of carbon united to two equivalents of hydrogen. After having previously

my description of the origin of coal, by attribating it to decomposed vegetable matter buried ander water

, you will see how fire damp has been produced. It has not arisen from the decomposition of coal now going on, but is the gas formed on the first entombment of the plants. Professor Graham found in his experiments that fire damp was composed entirely of light carburetted hydrogen, but it neither contained olefiant gas nor carbonic acid

, both of which Professor Bischoff had found in gases from mines in Germany. Dr. Lyon Playfair, in his paper on the gases evolved

during the formation of coal, published in vol. 1, p. 460, of the Meznoirs of the Geological Survey of Great Britain, confirtas Professor Graham's results in the following words :-" The general result of my analysis confirms the views formerly entertained of the composition of the gases, namely, that they form a mixtoure of light carburetted hydrogen with a small mixTure of nitrogen and oxygen, as common air, but that they neither contain olefiant gas nor carbonic acid gas, both of which Bischoff had found in the gases from mines in Germany." Probably olefiant and other gas may yet be detected in the gases from the coal mines of Great Britain, but up to this time they have certainly not been

noticed. Besides fire darup, sulphuretted hydrogen gas is sometimes found in coal mines abounding in brass or iron pyrites. It

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is composed of one equivalent of hydrogen, united to one of sulphur, and has a specific gravity of 1.1912. It is an explosive gas, and would be a dangerous enemy to the miner if it did not give decided evidence of its presence by its most disagreeable smell. Another most deadly gas found in mines where coal has been on fire, or where boilers are employed underground, is carbonic oxide, composed of one of carbon and one of oxygen; this gas is one of the most poisonous known, and, unfortunately, gives little evidence of its presence. Black-damp, choke-damp, or carbonic acid as it is respectively terined, composed of one of carbon and two of oxygen, is often found in badly ventilated mines, but it has not yet been proved to come out of the coal. Its specific gravity is 1.5290. After-damp, which is left in a mine after the explosion, is composed of nitrogen and carbonic acid.

A general impression prevails amongst working colliers that where flame exists there life can. This would be true as to an atmosphere of choke damp nearly pure, but if such a gas were mixed with nitrogen, a flame might burn and still a man be struck down. A flame also will burn in mixtures of atmospheric air and sulphuretted hydrogen gas, atmospheric air and carbonic oxide gas, when life will be instantly destroyed.

As it has been shown that fire damp was most probably formed at the same time as the coal in which it is contained, it will always be met with more or less in working of coal mines. In some inclined beds of coal outcropping at the surface without much cover, or lying on hill sides, the gas will gradually drain off; but in beds of coal lying in belts, separated by vertical or nearly vertical faults, the gas will be confined and pent up released by sinking shafts and working the seains, This shows the great care that ought to be observed in sinking to and working new fields so situated.

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