28 



for thi»; but lata- observers liave contented tKemselves -n-ith 

 upsetting all previous explanations, and confessing their own 

 ignorance. It was undei-stood, some time ag'i, tliat M. Arago 

 had succeeded at length in deducing the facts from the undulatory 

 theory; but his memoir, if ever published, I have unfortunately 

 not seen. Some remarkable appearances, though not difficult to 

 explain, offer themselves during a total eclipse of the sun, of 

 ■which a very interesting descrij^tion may be found in Huid's 

 Solar System. 



Gas Patents, by Henry Croft, D. C. t., Professor of Chemistry 

 in the University of Toronto. 



There is scarcely any branch of chemical manufectm-e which 

 Las attracted so much attention, and has been made the subject 

 of such numerous patents as that of coal gas ; we mention coal 

 gas alone, for although various proposals have been made, and 

 several carried into execution, for extracting a gas fitted for 

 illumination from numerous other substances; such for instance, 

 as oU, fats, rosin, bitumen, soap-suds, and even water, it does not 

 appear that any one of them can take the place of that from 

 which the gas was originally produced, viz, coal. 



Whether wo regard the convenience and utiUty of this illumi- 

 nating principle, or the enoimous saving of expenditure when its 

 tise is contrasted with that of all other ordinary combustibles, or 

 the numerous useful applications which have been made ; among 

 the most interesting of which may be mentioned the singeing of 

 cahco and of thread, formerly effected by much more clumsy 

 contrivances ; we cannot but consider this branch of manufacture 

 as one most deserving our attention and worthy of more especial 

 notice. 



Many improvements have been effected in various departments 

 of this manufacture, as may be seen from the fact of there having 

 been from sixty to seventy patents or specifications registered in 

 the Patent Office up to the year 1850. Since tliat time many 

 more have been entered, some of which wUl be briefly noticed 

 in the present paper. 



Although the general apphcation of coal gas to the purposes 

 of illumination may date from the commencement of the present 

 century, yet the knowledge of its properties was obtained at a much 

 earlier period. In lettere written in 1688-9, by Mr. Clayton, 

 Rector of Crofton, at Wakefield, in Yorkshire, addressed to 

 Robert Boyle, and afterwards to the Royal Society, we find a 

 tolerably accurate account of the method adopted by the author 

 for preparing a gas from coal, and also of its properties more 

 especially as regards its inflammabihty. 



Between 1770 and 1780 various experiments were made by 

 Hales and Watson on the production of an inflammable gas from 

 coal and other substances, but the first, though unsuccessful, 

 attempt at the apphcation of such product to useful pui-poses 

 seems to have been made by Lebon in France, during the years 

 1785-6. The substance employed by him was wood, which 

 does not yield nearly so good a gas as common coal, a fact which 

 may probably account for the faihire of his experiments. 



In the year 1792, Murdoch lighted his dwelling house with 

 gas, and in 1798 a gas-work was e.stabhshed in the factory of 

 Messrs. Bolton & Watt, with whom Murdoch was connectetl. 



For some yoai-s subsequent only a few pri\ato factories were 

 furnished with this valuable means of ilhuiiiiiation. It was first 

 applied to lighting streets in 1804, when Pall Mall in London 

 was furnished with gius, to replace the clumsy and inadequate oil 

 lamps, which all old residents in that city may romcniber. Since 

 that period the use of gas for this pur])ose has bocomo thoroughly 

 appreciated and most widely extended. 



GAS PATENTS. [1852, 



Gas which may be apphed to the purposes of illumination is 

 frequently found in nature, exuding either from the soil, or rock 

 or passing up with mineral waters. The hoty fires of Baku, the, 

 natural gas of Fredonia, (on Lake Erie,) the so called burning 

 springs above the British Falls, and at Hamilton, the burning 

 fountain of Dauphine, as weU as many others in various parts 

 of the world might here be mentioned. The gas which is thus 

 evolved is not, however, of the same natm'e as that obtained 

 artificiaEy from coal, although coal gas does, under cei-tain 

 circumstances, contain a very large proportion of the above 

 mentioned compound, and a very considerable quantity in all 

 cases. The evolution of this gas is not, therefore, to be taken as a 

 proof of the existence of coal, although in the coal mines it is 

 the substance which so frequently produces such calamitous 

 accidents, being generally known by the names of fire damp, 

 marsh gas, &c.* It appea.is that long before coal gas was 

 employed in England, the Chinese were in the habit of employ- 

 ing the natural product tor the purposes of illuminating and 

 heating. 



Before entering upon the improvements which have been 

 effected in the manufacture, it may be well to describe, in a few 

 words, the process as originally adopted, and the objects of its 

 several parts. The coal being heated strongly in cylindrical iron 

 retorts, gives off a mixture of various gases, together with cei-tain 

 oils, tar and water holding in solution several salts, principally of 

 ammonia. From these bodies the gas is purified, firstly, — by 

 traversing a large tube or reservoir called the hydraulic main ; 

 and, secondly, — by passing through a series of pipes kept cool by 

 a stream of water. The mixed gases are then conducted through 

 the purifiers, which are large vessels filled with a mixture of lime 

 and water; noxious gases, and some which are either not com- 

 bustible or do not give out any great light when burnt are thus 

 removed, and the so purified gas is then passed off" into the 

 gasometer or collecting vessel. 



In each of the processes above described great improvements 

 have been effected, while other contrivances have been attached 

 to the factory, either for the purpose of improving the quality 

 and illuminating power of the gas, or of rendering available, for 

 technical purposes, the different products obtained during the 

 process. 



The improvements may be classified under three heads: 



1st. As regards the quantity and quality of gas produced from 

 a given weight of coal. 



2nd. As regards the efficiency and economy of the purifying 

 process. 



3rd. As regards the illuminating power of the gas. 



The quantity of gas produced depends principally upon the 

 nature of the coal subjected to distillation, the finer cannel coal 

 yielding as much as 18,000 cubic feet of gas for every 100 oubio 

 feet of coal, while poorer kinds do not give more than 9000. 

 The quantity will also depend, to a considerable extent, on the 

 rapidity with which the coal is raised to a cherry-red heat; if 

 the coal be damp, and the heat raised slowly, a large quantity of 

 tar will be produced, much of which will distil oft' without pro- 

 ducing gas. The quality of the gas varies with the duration of 

 the process, during the first hour that substance which gives its 

 strong illuminating power to the gas is found to the extent of 13 

 per cent., while at the end of 5 hours there is only 7 per cent., 

 and at the end of 10 none at all, and the gas, consequently, 

 when bm-ning, gives out little or no light, defiant gas, (tho 

 illuminating principle) which burns with a brilliant white light, 



* The explosion which occurred some few weoki since, in « well on 

 Queen Sireel, Toronto, but which was fortunately not attended by any 

 •crious constqiiencxj, was undoubtedly owing to an escape of this gas from 

 ihc bottom ol the well. 



