28 Dr. Playfair’s Lecture on the Great Erhibition of 1851. 
. 
and the dyer no longer poisons the rivers with spent madder, but 
carefully collects it, in order that the chemist may make it again 
t for his use 
quote this instance as a remarkable example of the tendency of 
Chemistry to simplify processes of manufacture. The history of 
this salt is an exact parallel to that of Ho-ti and the pig. 
I might refer to the important discoveries of yellow and red 
triumphs of Chemistry in the dyeing of textile fabrics, whether 
of cotton, wool, and silk, or their mixtures; but I must content _ 
