104 



i$th March, 1881. 



The President, Professor Purser, in the Chair. 



Professor E. A. Letts read a Paper on 



RECENTLY-DISCOVERED ARTIFICIAL COLOURING 

 MATTERS. 



Professor Letts stated that the origin of the industry in arti- 

 ficial colours was the introduction of gas as an illuminating 

 agent. About the year 1739, the Rev. Dr. Clayton, Dean of 

 Kildare, obtained combustible gas by heating coal ; but the 

 inventor of practical gas-lighting was Murdoch, who, in 1792* 

 lighted his workshops at Redruth, in Cornwall, by its means, 

 and in 1 802 established a gaswork at the Soho Foundry, near 

 Birmingham, the property of the well-known firm of Boulton 

 and Watt. Ten years later the invention was introduced into 

 London, and gas-lighting soon became general. 



Every one knows that gas is produced by heating coal, and 

 that tar is obtained as a bye-product. Neither of these pre-exists 

 in coal, but both are produced from il by extremely complex 

 changes in the material of which the coal is composed. Now, 

 tar, which may be defined as the liquid substances produced by 

 heating coal, is a mixture of a great many very different bodies ; 

 over forty have been separated from it already, and no doubt 

 others remain to be isolated. In spite of the immense wealth 

 lying latent in coal-tar, it was at first regarded as a useless bye- 

 product, and was sent down the sewers or burned. But now it 



