626 HISTORY OF SCIENCE. 



and the variety and intensity of their hues. Many of the derivatives 

 of aniline were discovered and investigated by Hofmann and other 

 chemists, and their chemical relations determined simply as a matter 

 of science and without reference to practical applications. All these 

 researches were directed by the light of theoretical views. Benzol 

 was found to constitute the nucleus, or pivot, of an immense series 

 of compounds united in relations which were embodied in a very 

 ingenious and comprehensive theoretical view, for which science is 

 indebted to Professor KEKULE of Bonn. A large number of interesting 

 and useful substances belong to this extensive series, which has been 

 named the aromatic series on account of the number of fragrant prin- 

 ciples contained in it. In 1856 Mr. W. H. Perkin, of London, was 

 endeavouring to artificially prepare quinine by the oxidation of aniline. 

 He did not succeed in his aim, but he obtained the violet substance 

 now known as " mauve" Its intense tinctorial power, combined with 

 the beauty of its tint, struck Mr. Perkin, and he at once proceeded to 

 obtain a patent with a view to the introduction of the new substance 

 into commerce. He was successful in this, and " mauve " began to 

 be manufactured on a large scale. Hofmann's researches into the 

 aniline derivatives had pointed out their chemical relations, and it was 

 now also seen that other colouring principles might be derived from 

 aniline and made available as dyes. Hence the famous series of the 

 coal-tar colours, mauve, magenta, etc., and all their congeners. Coal- 

 tar, from having been a worse than useless by-product in gas manu- 

 facture, became the raw material of an extensive industry. It will be 

 observed that science has here done more than replace natural by 

 artificial production. She has produced substances which, so far as 

 we know, have no existence as natural products. There are many 

 thousands of substances not existing in nature which have been pro- 

 duced in the laboratory, and an unlimited number of such combina- 

 tions are possible. So that the coal-tar colours are not otherwise re- 

 markable than as an instance of this power of chemical science which 

 is popularly appreciable. The processes by which a substance like 

 benzol is made to yield highly complex bodies are such as would never 

 have been discovered without the guidance of a theory representing 

 at least a considerable number of the true relations of different sub- 

 stances. To discuss at large such relations or such processes would 

 be foreign to our present purpose, which must be confined to indi- 

 cating the form of the general principles of the science, rather than 

 presenting the matter of the science itself. This paragraph may, there- 

 fore, be regarded as a digression for the purpose of suggesting, by an 

 instance coming home to the general reader, the validity of modern 

 chemical theory as an instrument of investigation. 



We might mention scores of names of eminent men whose labours 

 and discoveries have advanced and are advancing the boundaries of 

 chemical science in every department. We are here, however, con- 



