MOLLUSCA. 145 



takes it with difficulty. Dr. Roth, appears to have 

 assured himself that the liquid extracted from these 

 snails becomes coloured under the influence of 

 light, and that the air has nothing to do with it ; 

 but I fancy both agents are active. The eggs of 

 these sea-snails are laid in June, and hang upon the 

 rocks in large balls. They have also a purple 

 colour. 



Researches similar to those just mentioned have 

 been made before. Long ago, Thomas Gage re- 

 ported that certain shells found near Nicoya, a little 

 Spanish town of South America, possessed all the 

 dyeing properties noticed by Pliny and other old 

 writers. They were employed for dyeing cotton on 

 the coast of Guayaquil and Guatemala. In 1686, 

 Cole made similar observations on the English 

 coasts. Plumier formerly discovered a colouring 

 snail in the Antilles, and Reaumur made repeated 

 experiments on common whelks (Bucdnum), which 

 he picked up on the coast of Poitou. Duhamel re- 

 peated these experiments on Purpura, found in 

 abundance on the shores of Provence. He and 

 Reaumur first noticed the extraordinary influence of 

 light in the production of the colour. Bixio studied, 

 though incompletely, the colour furnished by Murex 

 brandaris, and found it to be identical in properties 

 with that furnished by other gasteropod mollusca. 



The art of dyeing purple was continued in the 



L 



