16 REPOET— 1882. 



maximum. The application of gas for heating purposes has not been 

 encouraged, and is still made diflScalt in consequence of the objectionable 

 practice of reducing the pressure in the mains during daytime to the 

 lowest possible point consistent with prevention of atmospheric indraught. 

 The introduction of the electric light has convinced gas managers and 

 directors that such a policy is no longer tenable, but must give way to 

 one of technical progress ; new processes for cheapening the production 

 and increasing the purity and illuminating power of gas are being fully 

 discussed before the Gas Institute ; and improved burners, rivalling the 

 electric light in brilliancy, greet our eyes as we pass along our principal 

 thoroughfares. 



Regarding the importance of the gas supply as it exists at present, 

 we find from a Government return that the capital invested in gasworks 

 in England, other than those of local authorities, amounts to 80,000,000Z.; 

 in these 4,281,048 tons of coal are converted annually, producing 43,000 

 million cubic feet of gas, and about 2,800,000 tons of coke ; whereas the 

 total amount of coal annually converted in the United Kingdom may be 

 estimated at 9,000,000 tons, and the by-products therefrom at 500,000 

 tons of tar, 1,000,000 tons of ammonia liquor, and 4,000,000 tons of coke, 

 according to the returns kindly furnished me by the managers of many 

 of the gasworks and corporations. To these may be added say 120,000 

 tons of sulphur, which up to the present time is a waste product. 



Previous to the year 1856 — that is to say, before Mr. W. H. Perkin 

 had invented his practical process, based chiefly upon the theoretical 

 investigations of Hofman, regarding the coal-tar bases and the chemical 

 constitution of indigo — the value of coal-tar in London was scarcely a 

 halfpenny a gallon, and in country places gas-makers were glad to give 

 it away. Up to that time the coal-tar industry had consisted chiefly in 

 separating the tar by distillation into naphtha, creosote, oils, and pitch. 

 A tew distillers, however, made small quantities of benzene, which had 

 been first shown — by Mansfield, in 1849 — to exist in coal-tar naphtha 

 mixed with toluene, cumene, &c. The discovery, in 1856, of the mauve 

 or aniline purple gave a great impetus to the coal-tar trade, inasmuch 

 as it necessitated the separation of large quantities of benzene, or a 

 mixture of benzene and toluene, from the naphtha. The trade was 

 further increased by the discovery of the magenta or rosaniline dye, 

 which required the same products for its preparation. In the mean- 

 time, carbolic acid was gradually introduced into commerce, chiefly as 

 a disinfectant, but also for the production of colouring matter. 



The next most important development arose fi-om the discovery by 

 Grsebe and Liebermann that alizarine, the colouring pi*inciple of the 

 madder root, was allied to anthracene, a hydrocarbon existing in coal-tar. 

 The production of this colouring matter from anthracene followed, and 

 is now one of the most important operations connected with tar-distilling. 

 The success of the alizarine made in this manner has been so great that 

 it has almost entirely superseded the use of madder, which is now culti- 



