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pebbles lying upon and filling the inecjualitieis of its surface. 

 We have exposed here, ap[)arently, the original upper surface 

 of the nearly horizontal bed of niclaphyr. Care is required to 

 distinguish the segregations of jasper from the inclusions of 

 red felsite. Several small fragments of fclsitc similar to that 

 a hundred yards aw^ay, at the junction of Downer Avenue and 

 Crow Point Lane, and one mass a yard or more in diameter of 

 a slightly more granitic character, were observed imbedded in 

 the melaj)hyr, indicating very plainly that this ancient basic 

 lava broke through the still more ancient acid lava on its way 

 to the surface. The outcrop) in tiie street, as previously 

 explained, probably represents a knob or boss of felsite 

 [)rojecting through the flow of rnelaphyr where erosion has cut 

 most deeply into the latter. The extension on the general 

 map of these two belts of melaphyr eastward across Broad 

 Cove and Otis Hill to the harbor is, no doubt, somewhat 

 liazardous ; but no reason is apparent for terminating the 

 uielaphyr west of the shore, and its extension finds some, if 

 not sufficient, justification in the bowlders of melaphyr 

 ()bs(!rved on Button Island. The only rock observed in place 

 on this islet, as previously stated, is granite ; but the numerous 

 large and angular bowlders of amygdaloidal melaphyr on the 

 north and northwest shores prove that, although this rock does 

 not form part of the island, it nuist underlie the portion of 

 the harbor immediately to the northward. The melaphyr 

 forming these bowlders is similar to that in the vicinity of 

 Lincoln Street, being of greenish and reddish tints, coarsely 

 and distinctly amygdaloidal with epidote and quartz, and 

 exhibiting numerous irregular segregations or veinlets of the 

 same minerals. 



The great dike represented on the special map as extending 

 west from Downer Avenue across Planter's Fields Lane to the 

 eastern angle of the Huit's Cove melaphyr is probably the best 

 interpretation of the outcrops which it embraces. These are 

 all of precisely the same (character, a typical coarsely and 



