IGG Professor Thomas Thomson on Coal Gas. 



possesses the mechanical properties of common air, and which, there- 

 fore, he considered as not differing in its properties from common air. 

 That hydrogen gas was combustible, was known at least as early as 

 the beginning of the last century ; and many remarkable stories are 

 told by early chemists of the eighteenth century about its combusti- 

 bility, and the violent explosions which a mixture of it and common 

 air produced when brought in contact with a burning body. 



Dr. Black first showed, that carbonic acid, though a gas, differed 

 essentially from common air, and he gave it the name of fixed air, 

 because it existed in a solid state in the carbonates. Cavendish, in 

 1766, showed that hydrogen differs from common air and from car- 

 bonic acid. He examined its combustibility, its specific gravity, and 

 its peculiarities. In 1772, Dr. Priestley began his experiments on 

 air. First he examined carbonic acid and hydrogen ; then azotic gas, 

 then deutoxide of azote, muriatic acid gas, and ammoniacal gas. In 

 1774 he discovered sulphurous acid gas and oxygen gas, which was 

 destined to make such an alteration in the chemical theories of the 

 time. He discovered fluoric acid gas and carbonic oxide, though he 

 was not aware of its peculiar nature, and, indeed, remained ignorant 

 of it to the end of his life. 



It is curious that Dr. Priestley no where, so far as I know, mentions 

 carburetted hydrogen, or heavy inflammable air, as it was then called. 

 It constitutes the fire damp of coal mines. Its combustibility, and its 

 property of exploding with great violence in certain circumstances, 

 must have been known in coal countries at a pretty early period. In 

 the Philosophical Transactions for 1667, there is an account of a 

 blower of this gas passing through and taking fire from the flame of a 

 candle and burning briskly ; and in the same work, there are many 

 histories of explosions in coal mines, attended with the loss of many 

 lives. 



Though carburetted hydrogen occurs so commonly in coal mines, 

 and though it burns with a strong flame and gives out a good deal of 

 light, and although it had been ascertained that when common coal 

 was distilled at a red heat it gave out a great deal of inflammable gas 

 — it does not seem to have occurred to any person to employ it as a 

 substitute for candles, till the idea struck Mr. Murdoch, an Ayrshire 

 gentleman in the employ of Watt & Boulton. In the year 1808, he 

 published a paper in the Philosophical Transactions, pointing out the 

 advantages that would result from employing coal gas instead of oil 

 for illuminating the streets of towns and manufactories. 



In this paper he gives an account of the apparatus which he had 

 fitted up for lighting the cotton manufactory of Messrs. Phillips & Lee 

 at Manchester, which was at that time the greatest cotton mill in the 

 kingdom. He shows that the expense was only about one-fourth of 

 that of the candles or oil necessary to produce the same quantity of 

 light that the gas did. The coal used was the best Wigan cannel, a 



