370 ^f' Henry s Conftderations on different Materials, 



■ In the fubfequent part of this paper, we Ihall 

 proceed to confider the nature of the feveral 

 bafes ; endeavour to deduce a theory of 

 dying ; and, particularly, to account for the 

 aftion of the fubftances employed in the pre- 

 paration for the Turkey red, and in the other 

 parts of that procefs. 



PART SECOND. 



READ DBCEMBER ZJ , 1 786. 



IN the former part of this Memoir, it muft 

 have been evident to the Society, that the 

 proceffes which have been already defcribed, are 

 founded on chemical principles ; and that a know- 

 ledge of chemiftry muft, confequently, be advan- 

 tageous to thofe who have the diredtion of fuch 

 operations, and ferve to expedite improvements 

 in them. In thofe which remain for defcription, 

 the Hermetic Art, is equally ufeful. — The whole 

 bufinefs of dying, is, indeed, fo truly a chemical 

 procefs, or rather a combination of feveral che- 

 mical proceffes, that I am convinced the inven- 

 tion, or at leaft the principal improvements, of the 

 fundamental parts, muft have proceeded from 

 men fkilled in chemiftry. We have feen that the 

 Egyptians were even acquainted with the more 



com- 



