54 



water > and were left exposed to the external air above the , 

 coal stratum. The black clay, or aluminous ore, being the 

 cieling of the mine, absorbed the oxygen in the common air 

 by means of the sulphure of iron, (which is almost imper- 

 ceptibly mixed with it,) in such abundance as to expand it, 

 first in the form of white silky threads, merely separating 

 the laminae in a somewhat undulating form, but afterwards 

 Expanding it in such a manner, that the whole stratum, 

 ivhich was but 14 inches, sometimes became a yard in 

 thickness falling to the floor; and the threads, from being 

 scarcely perceptible, become near an inch long, curling in 

 many fanciful directions*. It sometimes ripens or consoli- 

 dates into what the workmen call native copperas, and may 

 possibly hold a little copper. It is somewhat crystallized, 

 like the green part figured, upon the clay or alumine, 

 which is in the act of throwing out little white opaque 

 round spots, the effect of a further change since the speci- 

 men was in my possession. These probably contain less 

 water than the other parts. — Its transparency is 2 or 3. Kirw. 

 This is a very good alum ore, the sulphuric acid and the 

 argil being by proper means separated, and recombined to 

 form that substance. 



Which will be shown in Piatt xxviii. 



