Rev. Mr. Gregor 071 the. Tremolite of Cornwall. 401 



Between the blocks which constitute the great mass of rock, 

 a compact substance of a greyish white colour, consisting of an 

 assemblage of crystalline spiculse diverging from centres, is found. 

 The same compact fossil occurs in the body of the rock, where 

 there has been no rent. This I found to be compact tremolite. 

 This substance assumes also another appearance of distinct and 

 separate crystallization. Crystals of it occur in the fissures of the 

 rock, in a state of promiscuous and thick aggregation. They are 

 about three-fourths of an inch in length, at the longest ; and consist 

 of thin, tabular, rectangular prisms, the angles of which are, for 

 the most part, rounded off, so that the section of the prism appears 

 to approach to a long ellipse. Some of these crystals possess a 

 vitreous lustre, and are semitransparent. In general their surface 

 is dull, as if from the effect of weathering, and they are of a 

 brownish ash colour resembling axinite. 



Before the strong jBame of the blowpipe, a fragment of a crystal 

 melts into a greyivsh enamel. At the temperature 69. Fahr. I found 

 the specific gravity of these crystals to be 3.20. 



I shall not trespass upon the time of the Society by recording the 

 minute detail of chemical experiments. I shall simply state the 

 mode of analysis which I pursued, and the final result of it, so that 

 I may furnish others with the means of judging whether I am war- 

 ranted in calling this mineral substance a tremolite. The propor- 

 tions of the several constituent parts of this fossil are given accord- 

 ing to an average taken from 1 00 grains of the distinct crystals. 



Acids produce very little effect upon the powdered crystals. No 

 effervescence was produced to indicate the presence of the carbonic 

 acid ; neither could I detect any other acid as a constituent ingredi- 

 ent, by means of fusion with pure carbonat of potash, neutralizing 



Vol. III. 3 e 



