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and slate south-west of the station, Prof. Niles has observed 

 angular fragments of slate actually enclosed in the granite, 

 though lying only a few inches from their original positions in 

 the parent bed. The induration, as if by heat, of the slate 

 and conglomerate at most points where they adjoin the granite, 

 and the frequent development of amygdaloidal characters in 

 the slate in those places, are also facts which tell strongly in 

 favor of the former igneous condition of the granite. The 

 evidence of the extravasation of the granite afforded by a 

 study of its relations to the uncrystalline rocks appears to be 

 sufficiently conclusive as regards the portions of granite imme- 

 diately involved. But since we know that the extrusion of 

 this rock occurred mainly at a period anterior to the depo- 

 sition of these uncrystallines, it is to the relations of the 

 different varieties of granite to each other and to the other 

 crystallines that we must look for proof of the exotic nature 

 of the granite taken as a whole ; and here the evidence is both 

 abundant and convincing. Following are the more striking 

 of the many proofs of the extravasation of the granite that 

 have come under my notice. At Hospital Point on the Bev- 

 erly shore, near the water's edge south of the lighthouse, is 

 a considerable mass of a distinct mica-slate enclosed in the 

 coarse, structureless granite. A smaller mass of a similar 

 stratified schist is enclosed in the granite near the northern 

 end of the railroad-cut in Beverly. On Marblehead Neck the 

 relations of the granite to the fine-grained, distinctly stratified 

 schist occurring there, are such as to leave no doubt that the 

 granite is exotic. Along the shore, at the south-western end 

 of the neck, the exposures are magnificent, and one can see, 

 especially at low tide, numerous angular, ragged, contorted 

 masses of the schist, of various sizes, enveloped by the 

 granite. Farther east, at the northern limit of the granite on 

 the eastern shore of the neck, a large dyke of this rock cuts 

 through the adjoining petrosilex. The granite composing the 

 small area of this rock on the west side of Wenuchus Lake, 

 in Lynn, is mingled with the adjoining petrosilex in such 



