336 THE ADDRESSES, LECTURES, ETC., OF 



improved burners, rivalling the electric light in brilliancy, greet 

 our eyes as we pass along our principal thoroughfares. 



Kegarding the importance of the gas supply as it exists at 

 present, we find from a Government return that the capital in- 

 vested in gasworks in England, other than those of local 

 authorities, amounts to 30,000,0.00?. ; 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 few 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, inas- 

 much 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 pre- 

 paration. In the meantime, 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 from the discovery 

 by Grgebe and Liebermann that alizarine, the colouring principle 

 of the madder root, was allied to anthracene, a hydrocarbon exist- 

 in " in coal-tar. The production of this colouring-matter from 

 anthracene followed, and is now one of the most important opera- 



