Localities of Minerals* 243 



Gypsum — Cayuga Lake. We are informed by Dr. L. Foot, 

 that the workmen who have excavated about 20 feet on the 

 border of the lake, in gypsum, which is generally of a dark 

 brown, or black colour, when they come to a transparent crya- 

 taUized piece, call it isinglass, and reject it as worthless : the 

 hint should be remembered by mineralogists, that the speci- 

 mens may be saved for their cabinets. 



ASBESTOS IN ANTHRACITE. 



Extract of a letter from Dr. I. W. Webster. 



Boston, 27th Nov. 1818. 



Dear Sir, 



In examining some masses of the anthracite from 

 Rhode Island, one piece attracted my attention, from the 

 waved structure of the lamellae into which it separated. The 

 fragments of this were Avedge-shaped, and I found the space be- 

 tween some of the laminaB filled up by a fibrous, silky sub- 

 stance, which induced me to break up other masses, in one of 

 which I discovered an abundance of amianthus ; the filaments 

 are of a light-green colour in some parts of the mass — in 

 others presenting different shades of brown. With a micro- 

 scope, I found the fibres intermixed with the anthracite ; or 

 forming thin layers, and these sometimes parallel to, at others 

 crossing, in different directions, the course of the laminas. 

 How far the presence of this mineral may influence the igni- 

 tion or combustion of the coal, is a question, perhaps, worth de- 

 termining. Should my engagements permit, I shall make fur- 

 ther examination, and inform you. In the mean time, the no- 

 tice of this fact may call the attention of some of your readers 

 to the subject. At any rate, this substance has, I believe, 

 never before been noticed in connexion with anthracite, aiid 

 is highly interesting in a geological point of view. 

 20 * 



