Jasper. 



267 



how easily it may be fused by the common blowpipe, into a white 

 semi-transparent enamel, containing bubbles : and I can have little 

 doubt but it ought to be referred to compact feldspar, which conducts 

 precisely in this manner before the blowpipe. I am inclined, how- 

 ever, to believe that it contains some argillaceous matter ; and it must 

 contain the red oxide of iron to give it its color. It occurs a few 

 rods east of the hill of varioloid wacke, which has been already de- 

 scribed, as composed of wacke and numerous nodules of compact 

 feldspar and limestone. Now I suspect that the action of granite on 

 this rock, has converted a part of it into this pseudo-jasper. For 

 granite appears in place only a few feet distant from the jasper ; 

 though the actual junction is hidden. If this be the true theory, then 

 the composition of the varioloid wacke is the same as that of the 

 jasper ; and since compact feldspar predominates in the former, it 

 probably does in the latter. And if I mistake not, very much of the 

 compact feldspar in the vicinity of Boston abounds in argillaceous 

 matter, as well as iron. In Hingham, indeed, it greatly resembles 

 the Saugus jasper, though of not so rich a color. 



13. Gray wacke Limestone. I have already stated the reasons that 

 induce me to believe the indurated compact limestone of Newport to 

 belong to the graywacke formation : and I have nothing more to add 

 in this connection. 



There is one other bed of limestone, which I strongly suspect 

 should be referred to this formation ; viz. in the west part of Walpole. 

 When I visited the spot, I had no suspicion that this rock had any 

 connection with the graywacke ; especially as I observed sienite 

 within a few rods of it. Nor do my notes furnish any very decisive 

 evidence either way as to this question. The dip of its strata, which 

 is about 45° N. W. is the most important circumstance. For I find 

 that the red quartz rock and talcose aggregate, which have been de- 

 scribed as occurring to the west of Walpole meeting house, have 

 nearly the same dip and direction, and are succeeded on the west by 

 sienite. Hence I suspect that the limestone, which lies two or three 

 miles southwest from those rocks, may be connected with them : 

 and especially when I recollect, that in all other cases where I have 

 found limestone connected with sienite, it is very white and destitute 

 of stratification : whereas that at Walpole, as already remarked, is 

 stratified and is of a gray color. Perhaps closer examination would 

 discover organic remains, (No. 494.) 



The bed of limestone in Bernardston is associated with argilla- 



