14 



stated, I have named, provisionally, the Naugus Head series. 

 In other words, the crystalline divisions of Eastern Massachu- 

 setts agree in composition and sequence with those established 

 in neighboring regions ; that this implies chronological equiva- 

 lence might fairly be questioned, and I do not assert it. 



NAUGUS HEAD SEKIES. 



Several small areas of the rocks referred to this series have 

 been marked on the accompanying map. 1 Of these, two are 

 of especial importance ; the first includes the city of Salem, 

 Salem Neck, the islands of Great Misery and Little Misery, 

 Baker's Island, Naugus Head on the north end of Marblehead, 

 various small islands between Marblehead and Great Misery, 

 and several narrow strips along the Beverly shore ; while the 

 second area embraces all but the seaward end of Large Nahant. 

 A glance at the map will show that these areas lie contiguous 

 to the sea-shore ; and this fact — since these shores are for the 

 most part rocky — has enabled me to trace their boundaries 

 with considerable accuracy. In Salem and Peabody, however, 

 the rocks marked as belonging to this series seem to have 

 been more or less fluent, and are blended with the diorites of 

 the Huronian formation in inextricable confusion ; which, to- 

 gether with the absence of outcrops north of North river, has 

 rendered the determination of the western boundary of this 

 area difficult ; and the line as laid down on the map is partly 

 hypothetical. 



The rocks of this series, though frequently stratified, appear 

 in general to have been somewhat fluent, and usually exhibit 

 more or less extravasation ; but doubtless in some cases the 

 metamorphic action has stopped short of this extreme term, 

 though destroying all traces of bedding. In many places, as 

 notably on Winter Island and Great and Little Misery, the 

 entire formation seems to have been plastic, and the extravasa- 

 tion has been so extensive that the character of the rock 



1 See post., p. 23. 



