388 DR T. THOMSON on Asbestus, Chlorite, and Talc. 

 pound of, 



10 atoms bisilicate of alumina, 

 1 atom bisilicate of potash, 

 4 atoms water. 



Agalmatolite approaches most nearly to nacrite in its compo- 

 sition. It differs by containing 1 atom bisilicate of potash, and 

 4 atoms water. Nacrite is an anhydrous bisilicate of alumina, 

 and agalmatolite may be considered as a hydrous bisilicate, 

 mixed or combined with a little bisilicate of potash. 



I intended in this paper to have investigated likewise the 

 chemical constitution of Steatite ; but I have already trespassed 

 so far upon the usual length of papers presented to the Society, 

 that I think it better to delay that part of the subject to a fu- 

 ture opportunity. 



