PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 843 



Diabase and grit.] 



No. 2129. GRIT. ("Volcanic.) 



Taylor's Palls, corner of Government and West streets, 200 feet above the river. 

 Ref. Annual Report, xxiv, page 41. 



Meg. Granular, siliceous, greenish, in sedimentary structures. 



Nie. Named in order of abundance the ingredients of this rock are epidote, 

 quartz, leucoxene( ? ) , devitrified glass; these are in rounded forms, but the rounded 

 forms are themselves composite, especially the quartz, and made up of a great many 

 interlocking grains. The epidote is also of irregular shape in some instances, but it 

 has the appearance, for the most part, of having been accumulated as a part of a beach 

 sand. There are also variable amounts of hornblende, urttnolite (secondary fibres 

 growing from the hornblende and piercing the quartzes) and rounded pebbles of 

 diabase. In the last are sometimes grains of epidote, which seems to show that the 

 epidote was generated before it was made a constituent of this grit. Much of the 

 quartz is pneumatolitic since the accumulation of the debris. Three sections. 



Age. Keweenawan. N. H. w. 



No. 2129 A. GRIT. ( Volcanic.) 



Same place as No. 2129. 



Ref. Annual Report, xxiv, page 44. 



Very fine and almost flinty condition of the same rock as No. 2129. 

 Consists of tine angular grains of quartz and epidote. One section. 

 Age. Keweenawan. N. H. w. 



No. 2131. GRIT. (Epidotic.) 



Taylor's Palls, 250 to 300 feet above the river. 

 Ref. Annual Report, xxiv, page 44. 



Meg. Irregularly cavernous and associated with fine-grained epidotic and 

 quartzose rock, somewhat resembling No. 2129, but of a different composition, as it 

 contains also much fine, fragmental feldspar. In the midst of this is a piece of volcanic 

 glass, now changed (excepting its minute feldspars) to an isotropic chloritic substance. 

 One section. 



Age. Keweenawan. N. H. w. 



No. 2132. DIABASE AND GRIT. 



Taylor's Palls, 1,030 to 1,040 feet above the river, near the summit. 

 Rff. Annual Report, xxiv, page 45. 



Compact diabase, more or less porphyritic, seamed by a fine, greenish 

 rock resembling No. 2129A or No. 2131, the widest seam being three-fourths of an inch. 



Mic. The slide is composed of two different rocks, viz.: very much altered 

 (weathered) porphyritic diabase and a granular mixture of fine quartz and epidote, 

 evidently of clastic structure and origin, the latter forming thin greenish seams in 

 the former. One section. 



Aye. Keweenawan. 



