540 GAS, COAL 



GAS, COAL. Although the employment of gas for illuminating purposes can be 

 traced back to remote periods 6f antiquity, yet the substantial history of this appli- 

 cation may be related in few words. In various places and at different times issues of 

 inflammable gas from the earth have been observed ; the holy fires at Baku on the 

 shores of the Caspian Sea, und those of Pietra Mala in Italy are instances ; but such 

 issues have usually been only regarded with superstitious dread by the ignorant people 

 who have observed them. The Chinese alone, if we are to believe the accounts of 

 that boastful people, have many centuries ago turned these natural sources of in- 

 flammable gas to useful account, and have rendered them available both for heating 

 and illuminating purposes. Abundant sources of inflammable gas exist in the coal 

 districts of this country ; and in some localities, as at Chat Moss in Lancashire for 

 instance, so easy is this gas procurable, that it is only necessary to plunge an iron rod 

 a few yards deep into the soft peat, and then on its withdrawal to insert a tin tube, 

 in order to secure a copious discharge of gas, which is evolved in a continuous stream 

 at a high pressure, and apparently for an unlimited period of time. But as this gas 

 consists of nearly pure light carburcttod hydrogen, and contains no luminiforous con- 

 stituent, it yields scarcely any light when burnt in the ordinary manner, and cannot 

 therefore be rendered available for illuminating purposes. It has, however, boon 

 successfully employed as a source of heat, and a jet of it was long made use of as the 

 sole fuel to heat a four-horse boiler used for agricultural purposes. As early as the 

 year 1659 Mr. Thomas Shirley communicated to the Royal Society a paper describing 

 some experiments upon an inflammable gas issuing from a well near Wigan in Lanca- 

 shire, and nearly a century later the Rev. John Clayton, having noticed the same 

 phenomenon in the same locality, and finding on digging a few feet into the soil, that 

 the gas issued from a bed of coal, he was led to try whether a similar gas could not 

 be obtained artificially, by exposing coal to heat in close vessels. He succeeded in 

 obtaining an illuminating gas, and amused his friends by collecting it in bladders and 

 burning it from a hole pricked in the bladder. The particulars of these experiments 

 Mr. Clayton communicated to the Royal Society in the year 1739. But he does not 

 appear to have thought of applying his discovery to any practical purpose ; and it was 

 not until 1792 that the gas thus artificially obtained was used for illumination by 

 Mr. Murdock, who first lighted his house and office at Redruth in Cornwall, and 

 afterwards, having made several improvements in the apparatus, ho lighted the factory 

 of Messrs. Boulton and Watt at Soho about the year 1804, and in 1805 the largo 

 cotton mills of Messrs. Philips and Lee at Manchester ; those of Mr. Lodge at Halifax 

 having been lighted about the same time by Mr. Clegg, a gentleman to whose energy 

 and scientific skill gas-lighting, in its earlier stages especially, is much indebted. In 

 the year 1810 the Act of Parliament incorporating the London and Westminster 

 Chartered Gas-light and Coke Company was passed, and, on the 31st of December 

 1813, Westminster Bridge was lighted with gas. This step was soon followed by the 

 introduction of gas in the place of oil in several of the chief thoroughfares of the 

 metropolis. From that period the progress of this branch of the chemical arts has 

 been extremely rapid and satisfactory, so far at least as the extension of the manu- 

 facture and the improvement of the mechanical part of the processes are concerned. 

 Nevertheless, although the methods employed for the generation and purification of 

 gas have been rendered more economical, it can hardly be said that the average of the 

 gas, supplied to consumers in London and the provincial towns, is either purer or 

 better in quality than that furnished in the earlier years of the manufacture. 



Before proceeding to describe the actual processes now employed for the generation 

 of illuminating gas, it will be advisable to consider briefly the general scientific prin- 

 ciples involved in those processes, and especially the chemical relations of the materials 

 employed for the generation and purification of illuminating gas, together with the 

 bearings of , chemistry upon the operations of generating, purifying, and burning such 

 gas. 



The chemistry of gas manufacture. The chief materials employed in the manufac- 

 ture of gas for illuminating purposes are coal, oil, resin, peat, and wood. Theso 

 materials, though very dissimilar in appearance, do not essentially differ from each 

 other in their chemical constituents ; they may all be regarded as consisting chiefly of 

 the elements, carbon, hydrogen, and oxygon, and their value for the production of 

 illuminating gas increases with the increase of the proportion of hydrogen, and with 

 the diminution of the relative amount of oxygen. Accordingly wo find that oil and 

 resin generally produce gas larger in volume and better in quality than coal, whilst 

 peat and wood, owing to the largo proportion of oxygon which they contain, are 

 greatly inferior to coal for the purposes of the gas-manufacturer. The relative pro- 

 portions of carbon, hydrogen, and oxygon, in the organic part of these substances, is 

 seen from the following comparisons : 



