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MUSEUM OF COMPARATIVE ZOOLOGY. 



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quarry. Several layers contain distinct fragments of trap, rather an- 

 gular in form, and variable in structure from dense to vesicular. These 

 layers are darker than the normal red sandstone, some being nearly 

 black, presumably on account of the trap sand they contain; some 

 might be mistaken for metamorphosed sandstone, as they have faint 

 bedding, and in a rough way resemble trap ; but they grade into normal 

 reddish sandstone below as well as above, and this clearly shows that 

 their color is not due to metamorphic action. There is a strongly slick- 

 ensidcd joint at right angles to tho dip in this (piarry, with some evi- 

 dence of a fault of several feet throw. 



Hitchcock wrote (e, 442) that a tufaceous conglomerate "reposes on 

 the greenstone on the east side of Mounts Tom and Holyoke ; and con- 

 sists of a mixture of angular and rounded masses of trap and sandstone, 



with a cement of the same materials I do not doubt but the same 



rock may be found on the east side of nearly all the greenstone ranges 

 in the Connecticut Valley. Its thickness is but small, and it graduates 

 on one side into greenstone, and on the other into sandstone." This 

 evidently refers to ,a bed similar to those above described, and points to 

 the same conclusion. He refers to it again in the Ichnology {h, 17). 

 Lyell (a, 794) visited this region in his company, and concluded "that 

 there were eruptions of trap accompanied by upheaval and partial denu- 

 dation, during the deposition of the red sandstone." Da:.a quoted Hitch- 

 cock's results in 1863, and added, "But after an examination of the 

 region the author regards it more probable that the appearance of scoria 

 is owing to an escape of steam laterally from between the opened strata 

 during tho ejection of the trap of the adjoining mountain," {b, 430.) 

 Emerson's observations, made recently (196), confirm Hitchcock's and 

 those of the present writer. In his last edition of the Manual (1880), 

 Dana makes no mention of overflows. 



C. West Sprmgfieldj Mass. (fig. 38). — About two miles west of this 

 station on the Boston and Albany Railroad, the track passes through a 

 short cut in the second posterior trap ridge near its end on the north 

 bank of the Wcstfield Eiver, and fortunately reveals some twenty feet 

 of sandstone below the trap, as may be seen even from a passing train. 

 The natural outcrops in this neighborhood are very poor, as the ridge is 

 almost smothered in the high sand plain of the Connecticut River. The 

 main ridge and the first posterior are also very poorly shown as far as 

 critical outcrops arc concerned, though the trap itself is well opened in 

 the city quarry by the railroad on the west face of the main ridge, where 

 distinct columnar structure is apparent. In the railroad cut, it is 



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