Il8 HENRYS. WASHINGTON 



graphic texture, which are highly characteristic and very 

 abundant. 



The provenance of these blocks is not known, but they prob- 

 ably come from a dike in the immediate vicinity. Search 

 revealed an outcrop of a dense, very pale gray dike, with only a 

 slight tinge of blue, near a small pond across the road. This is 

 evidently a bleached-out solvsbergite, since the microscope 

 reveals the fact that the small, originally blue, hornblendes are 

 nearly all entirely decomposed to an opaque black substance, 

 with little change of form, and small crystals of diopside are 

 also possibly derived from them. This rock also shows the 

 peculiar and striking micrographic patches, and it is therefore 

 highly probable that the wall blocks were obtained from freshly 

 blasted portions of this dike. 



Only two analyses have been made by me of these rocks, 

 which are given below. For comparison there are quoted an 

 analysis of the Coney Island dike recently published by Rosen- 

 busch, as well as two analyses of Norwegian solvsbergites. 



100.33 100.04 99-85 100.53 99.60 



I. Solvsbergite. Dike 184, Andrew's Point, Cape Ann. H. S. Washington anal. 

 Amer. Jour. Sci., (4) VI, p. 178, 1898. 



II. Solvsbergite. Dike. Coney Island, Salem Harbor. H. S. Washington anal. 



III. Solvsbergite (" Bostonitic Alkali-syenite-Porphyry "). Coney Island. M. 

 Dittrich anal. Rosenbusch, Elem. d. Gest. lehre., 1898, p. 199, No. 3. 



IV. Katoforite-Solvsbergite. Lougenthal, Norway. L. Schmelck anal. Brogger, 

 op. cit., I, p. 80. 



V. Aegirite-Solvsbergite. Solvsberget, Gran, Norway. L. Schmelck anal. 

 Brogger, op. cit., p. 78. 



