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COAL MINES OF

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coal into glance-coal, which is devoid of bitu-men, and combined with a proportion of earth.

This coal yields carbureted hydrogen gasof much less density than that obtained fromother coals.* The number of theories howeverupon the origin of coals are yet very nume-rous, and leave much room for further inves-tigation.

Coal, when decomposed by heat, givesout acidulous water, oily bitumen, charcoal orcarbon, carbureted hydrogen, and carbonicacid; and as these are the principal bases ofits formation, the researches of philosophyconverge in their examination, and point outthe extreme necessity of science and cautionin the working and management of collieries.

The principle most destructive to the secu-rity of coal mines, and the lives of the miners,is the inflammable air, fire-damp, .or carbu-retted hydrogen gas, which consists of hydro-gen holding some carbon in solution ; and, ac-cording to Dr. Thomson, contains three-fourthsof its weight of carbon, and one-fourth of hydro-gen. This is contained in every stratum, andliberates itself from the secretions of nature in

* Dr. Henry’s Elements of Chemistry;

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