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gneisses. Strike S. 20°-70° E. Judging from the nature of 

 the drift, this area extends south-westerly into HoUiston. 

 The area in 'Dover is less gneissic and more felsitic, consisting 

 of alternating bands of diorite of various textures, and horn- 

 blendic felsites, and passing on the south into the "mixed" 

 series. Stratified Huronian rocks, other than petrosilex and 

 felsite, are of rare occurrence south of the Charles River, Be- 

 sides those last mentioned, I know of only one instance worthy 

 of note. This is on the Cohasset shore, between Black Rock 

 and Little Harbor, and has been described in connection with 

 the granites. 



Returning to our starting point in Essex County, however, 

 and looking north-easterly, we find several important areas of 

 bedded rocks. Along the road running from Lynnfield Centre 

 north-westerly are many croppings of interstratified quartzites, 

 and fine-grained, often aphanitic, or slaty-looking, diorites. 

 These continue for one and a half miles, and are met in the 

 direction of North Reading by the unstratified diorite. The 

 rocks in this section are almost identical with those in Reading, 

 and the strike and dip are the same. Between Lynnfield Centre 

 and Middleton the rocks are rarely exposed ; but in traversing 

 this region I have observed that the boulders in the drift, espe- 

 cially the larger and more angular ones, which evince the least 

 transportation, consist largely of imperfect gneisses and strati- 

 fied diorites. These rocks are quite distinct from those in the 

 direction of North. Reading, but closely resemble the gneiss in 

 Wayland ; and, like the Wayland rock, they are possibly, but 

 not probably, Montalban, The stratified rocks in southern 

 Middleton are probably more abundant than I have ventured 

 to represent them. 



The long and narrow stratified belt beginning at the Salem 

 and Lowell R.R. in Peabody and reaching into Wenham is 

 based mainly upon observations made by Prof. Hyatt. The 

 strike is parallel with the belt, and both are, perhaps, a 

 little more easterly than represented. The dip is 60° and 

 upwards to the north-west. The only rocks observed here are 



