152 



GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



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That the enstatite can have passed from the western enstatite rock into 



tlie limestone is improbable, 

 for the iifty feet nearest to 

 the enstatite rock contain 

 much less of the enstatite 

 than do the next thirt}-. 



At Downey's the white 

 limestone is free from ensta- 

 tite, and the contact with 

 the enstatite rock is covered 

 Wii ' /'*>iN //V ^ V^ X*^ V"^ -■ ■= ^'^ ^^'® swamp. At Munn's 

 l|W^)/ ,/ \y^i^/^ ^>3n. ^Wirv"M 1 brook the enstatite-limestone 

 *^ ■ ' "" mixture is less in anvmnt, 



and the enstatite so pre- 

 dominates that I tried to 

 explain the whole by assum- 

 ing that the black serpen- 

 tine (or enstatite rock) was 

 an igneous rock, and that the 

 serpentine-calcite mixture 

 (which in altered surface 

 specimens could not be 

 studied so well as in the 

 fresh masses opened in the 

 AVestfield quarry) was de- 

 rived from the eruptive rock 

 by the removal of some 

 allotriomorphic constituent 

 and the interstitial develop- 

 ment of a later secondary 

 calcite in its place. A sin- 

 gle look at the great blocks 

 of the black spotted marble 

 in the quarry will })revent 

 one from deriving this hun- 

 dred feet of limestone from 

 any alteration of an eruptive like that from wdiich the black bed may have 



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