Portland and its Vicinity, 313 



nodules of much size. A good deal of the plumbaginous 

 mica slate on Cape Elizabeth, as has been remarked in 

 another place^is in like manner impregnated with pyrites. 

 Upon the whole, I cannot see why the vicinity of Port- 

 land, especially JewelPs Island, does not present a good 

 situation for the manufacture of alum and copperas. 

 What practical difficulties may present themselves, I 

 cannot say. But appearances are certainly quite favor- 

 able. 



We do not go far back from the coast in the vicinity 

 of Portland, before we find that the rocks which have 

 been described, are succeeded by gneiss. As we go west- 

 erly from the city, however, towards Saco river, I have 

 good reason for supposing that the slates increase in 

 width, as represented on the map ; although I have not 

 given that region a thorough examination. 



1 picked up a pebble of quartz rock on Jewell's Island, 

 twice the size of the annexed drawing, which presents a 

 tolerably good example of a peculiarity in the structure 

 of this rock, which I have often noticed in other parts of 

 New England. I refer to the evident traces of a me- 

 chanical, or at least semi-mechanical origin, which some 

 parts of the mass present ; and which, in the pebble ex- 

 hibited below, shows itself in the angular fragments in 

 the upper part, scattered through a darker colored and 

 apparently somewhat ferruginous cement- The quartzose 

 layers of the specimen seem to have been more or less 

 broken and moved, and afterwards very firmly cemented 

 together. The latter process does not seem so difficult 

 to explain ; but what was the nature of that force which 

 could have been so powerful as to break hard quartz into 

 such fragments, and yet scarcely remove them from their 

 places, I confess myself unable to imagine. Specimens 



VOL. I. PART III. 41 



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