A CONTRIBUTION TO THE GEOLOGY OF SOUTHERN MAINE 527 



It is thought to be in the interest of accuracy to publish these 

 duplicate analyses precisely as they were made. A better 

 summation would have been obtained by making a composite of 

 the two. 



Microscopically the rock is characterized by shreds of biotite 

 with parallel orientation, giving a typical schistose structure. 

 Quartz, orthoclase, a plagioclase near the albite end of the series, 

 brown hornblende and a very little augite make up the rest of 

 the rock, with a little accessory magnetite and apatite. The 

 pyroxene is of the common augite variety, slightly \ r iolet tinted 

 from titanium ; it is usually twinned, but with no crystal boun- 

 daries. The whole is much strained, the feldspars being cracked 

 with minute fissures all parallel to each other, the cracks being 

 filled with sericite. The quartz is decidedly granular. 



A specimen from Rutherford Island, given to the writer by 

 Dr. Bascom, is evidently of the same type of rock, but in thin 

 section contains a larger proportion of ferro-magnesian consti- 

 tuents and among these a larger proportion of brown hornblende. 



The balance of evidence is that these schists are completely re- 

 crystallized, highly metamorphic sediments, original^ of the 

 composition of arkose. The presence of the augite is the 

 strongest point against this origin. 



Turning to the igneous rocks, there is evidence of at least two 

 periods of intrusion. The first of these antedated the meta- 

 morphism of the region. In the field these appeared to present 

 all variations in composition, grading from extreme basicity to 

 extreme acidity. Granite-gneiss, diorite, anorthosite, mon- 

 zonite, gabbro, hornblende schist and peridotite are a few of the 

 varieties. Analysis reveals the fact that these are not so widely 

 separated as they appeared, and that the majority belong among 

 the intermediate types. Cutting the above-mentioned rocks are 

 numerous less metamorphosed pegmatites and aplites which were 

 not studied by us in detail. 



Of later age is a series of diabase dikes. These follow joint 

 planes for the most part and belong to two series, one trending 

 N. 85 E. the other N. io° E. The physiographic effect of these 

 dikes has already been mentioned. 



The classification adopted is the quantitative one recently 



