74 ANNUAL OF SCIENTIFIC DISCOVERY. 



mitted to a gentle heat, a most beautiful and delicate pink color resulted. 

 Subsequently, murexide was employed and applied successfully by Mr. De- 

 pouilly, of Paris, to dyeing wool and silk, and to printing: calicoes, by the 

 aid of oxide of lead and chloride of mercury as mordants; but the great 

 obstacle to its extensive use was the difficulty of obtaining uric acid in suffi- 

 cient quantity for its manufacture. The idea soon occurred to chemists to 

 extract it from guano; and this is the curious source whence the chief sup- 

 ply of uric acid is obtained, and which enables Edmund Potter, Esq., and 

 other printers, to produce the color called Tyrian purple. 



Another example will be found in the successive scientific discoveries which 

 have led to the discovery of the recently popular color, mauve. Lichens, 

 which have been the subject of extensive researches on the part of Robi- 

 quet, Heeren, Sir Robert Kane, Dr. Schunck, and especially of Dr. Stenbouse, 

 have yielded to those chemists several new and colorless organic substances, 

 which, under the influence of air and ammonia, give rise to most brilliant 

 colors, and amongst these are orchil and litmus. Dr. Stenhouse, in a most 

 elaborate paper published by the Royal Society in 1848, pointed out two im- 

 portant facts : first, that the color-giving acids could be easily extracted from 

 the weed by macerating it in lime- water, from which the coloring matters 

 were easily separated by means of an acid; and, secondly, the properties of 

 certain coloring acids, which gave M. Marnas, of Lyons, the key which ena- 

 bled him to produce commercially from lichens a fast mauve and purple, 

 which, tip to 1857, had been considered impossible of attainment. 



The commercial production by Mr. W. H. Perkin of another purple at the 

 same time is not less interesting. Some thirty or forty years ago, Dr. Runge 

 obtained from coal-tar six substances, amongst which was one called kyanol, 

 which substance was thoroughly examined by Dr. Hoffman, who proved it 

 to be an organic alkaloid, and identical with a substance known as aniline. 

 Owing to the subsequent study of this substance by this chemist, and the 

 discovery that it yielded a beautiful purple color when placed in contact with 

 bleaching powder, his pupil, Mr. Perkin, was induced to make experiments 

 with a view of producing commercially a fast purple, in which he succeeded. 

 The process devised by this chemist is exceedingly simple, and consists in 

 oxidizing aniline by means of bi-chromate of potash and sulphuric acid. 



More recently, M. Renard found a method of producing also from aniline, 

 by means of chlorine compounds, a most splendid rose color, called by him 

 fuchstachine; and within a few months Mr. Price has also succeeded in pro- 

 ducing from aniline, by the employment of peroxide of lead, either a fast 

 purple, or a pink, called by him roseine, and a fast blue, according to the 

 mode of operating. All these colors require special mordants to fix them on 

 calicoes or muslins, such as albumen, lactarine, and other azotized principles. 



In concluding, I cannot give a better idea of the immense magnitude of the 

 calico-printing trade of Great Britain, than by quoting the number of yards 

 exported, which amounted in 1858 to nearly eight hundred millions. 



MINIATURE AND ENAMEL PAINTING. 



Painting in miniature is in danger of becoming one of the lost arts. Pho- 

 tography has been carried to such a degree of perfection, is so accurate as to 

 mere likeness, and is, withal, afforded so cheaply, that it is rapidly taking 

 the place of portraits upon ivory. Artists who have hitherto devoted them- 

 selves to this branch of the art are now either turning their attention to 



