Origin of Argentine. 



307 



ceous limestone. These rocks appear to be merely the fragments 

 which adhered to the granite, when it was raised through the slates, or 

 when these were torn off from the granite. Most of the layers are 

 perpendicular : but some of them towards the eastern side, are much 

 bent and become almost horizontal. Here the argentine, a a, appears, 

 lying for the most part between the slate and the granite ; penetrating 

 both rocks, indeed, a short distance, but not forming what ought to 

 be called a vein in either. It does not enter the granite, as far as I 

 could ascertain, but a few inches. And it is that part of the slate 

 which lies in the vicinity of the argentine which is micaceous lime- 

 stone. 



Argentine with Mica Slate and Granite : West Hampton. 



Now my hypothesis is, that when the granite was protruded into 

 the mica slate and coarse limestone, while in a melted state, its heat 

 by decomposition or sublimation, or both, forced the carbonate of lime 

 into the cavities that were produced by the elevation of the rocks, 

 where it assumed the form of that very pure variety of carbonate of 

 lime called argentine, or slate spar. Whether its intrusion among 

 the sinuosities of mica slate caused it for the most part to assume a 

 similar structure, I do not undertake to decide. Nor do I feel much 

 confidence in any part of this hypothesis, though it seems to me wor- 

 thy of consideration. 



In Vermont limestone is found among the layers of argillaceous 

 slate. Here it is destitute of mica, and is mixed with the argillace- 

 ous slate in such proportion as scarcely to be distinguished from 

 it, except by its effervescence with acids : yet it appears to be closely 

 allied to micaceous limestone. 



