Protrusions of Granite. 



427 



On the northeast side of mount Tom, on the bank of a small stream 

 and close by a saw mill, which is only a few rods from the stage road 



rock in the vicinity is the variegated sandstone. In one place we see the strata of 

 sandstone bent upwards and the granite beneath. 



" You are doubtless acquainted with the important observations of J. Hall, 

 in Galloway in Scotland. Veins of granite, a a, &c. have penetrated the transi- 

 tion argillaceous schist, b 6, &c. enveloping also the fragments, c c c, of the same, 

 and overspreading the schist in part. The schist has suffered numerous distur- 

 bances from the influence of the granite and is changed at the place of contact by 

 the volcanic he^t. 



" You speak of your greenstone. Is it diorite or dolerite ? From your descrip- 

 tion I suspect it to be diorite,* that is, a greenstone into whose composition amphi- 

 bole enters, and not pyroxene. 



In the Hartz facts occur similar to those which you have observed. I shall be 

 much obliged to you when you send another box of minerals for exchange to the 

 Comptoir, to put in some specimens of greenstone, that I may institute a compari- 

 son. In the Hartz we see that the diorite assumes an amygdaloidal texture, be- 



* After what I have written on this rock, it is hardly necessary to say that this 

 conclusion is correct. 



