320 Sketch of the Geology of 



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there are many exceptions. It is the granitic gneiss that 

 more commonly dips at so small an angle. 



Before describing the upper unconsolidated strata 

 arouqd Portland, I may as well notice two or three 

 varieties of unstratified rocks in the same region. 



Granite and Sienite. 



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Under hornblende slate I have already stated all that 

 I know of the sienitic deposits in the southwest part of 

 Maine. Around Portland I have met with nothing that 

 deserves this name, except a few boulders, near the 

 tower in the north part of the city, of great beauty. The 

 mass of the rocks is feldspar, of a much whiter color than 

 in the sienite of Quincy and Cape Annj and through 

 this base are disseminated brilliant foliated masses of 

 black mica and hornblende. I shall show, further on, 

 that the proper place to look for this rock in place, is 

 several miles north of the city. Should it be discovered 

 in large quantity, I feel sure it would be greedily sought 

 after for architectural purposes. 



Genuine granite is a rock of rare occurrence in the 

 vicinity of Portland. In approaching the gneiss from 

 the city, that is, in passing northwesterly, we meet with 

 some veins and irregular intruding masses of this rock, 

 while the slate exhibits that more decidedly crystalline 

 aspect which is so common in the vicinity of granite. In 

 the gneiss also, are numerous veins of coarse granite. 

 But I discovered no large deposite ; although not im- 

 probably such may exist in some part of the gneiss forma- 

 tion. I have also seen good specimens of granite from 

 the eastem part of Maine. Yet much of the rock that 

 is quarried under this name is genuine gneiss. I am 



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