400 Rev. W. Gregor oji the Tremolite of Cornwall. 



striking feature in the neighbouring country. Blocks of the same 

 species of rock are scattered about in different parts of the hill and 

 in its vicinity. 



This rock is of dark bottle green colour. All the specimens of it 

 do not possess an uniform degree of hardness : they vary also in 

 respect of fracture. The harder species frequently assumes that 

 wavy and polished exterior surface which characterizes the magne- 

 sian stones. It is sufficiently hard to scratch glass. It has an un- 

 even and sharp edged or splintery fracture, which exhibits no 

 lustre. Upon examination of its surface with a pocket microscope, 

 it appears to consist of a very fine-grained uncrystallized substance 

 of a blackish green colour, interspersed with thin laminse of pre- 

 cious serpentine of a green colour. The rock of the softer species 

 seems to be composed of these two substances also. It has a few. 

 small greyish white specks scattered over it : these are occasioned 

 by some softer substance imbedded in it. I am inclined to think 

 that this substance is compact tremolite. The softer species of 

 rock may be scratched with the nail. It has an uneven fracture, 

 inclining to earthy. This rock abounds with iron, insomuch that 

 the magnet is enabled to attract very small particles of it. It re- 

 sists a very strong flame of the blowpipe without being fused. The 

 fine edges however of the harder species seem to yield a little to 

 its action. 



In the side of the hill, below the ridg« of rock, a quarry Is 

 opened for the purpose of supplying the neighbouring road with 

 stones. Here the rock is laid bare in large" masses. It is accom- 

 panied in some places with asbest, and also with a fine white 

 earth, which appears from the filaments which are mixed with it, 

 to consist of asbest broken down in a state of partial decomposi- 

 tion. 



