86 THE CANADIAN NATURALIST. [Vol. ix. 



schistose beds of mica schist and hornblendic schist and is part 

 of a series of metaniorphic strata. From a hand specimen either 

 of these rocks would be pronounced eruptive ; but observation 

 in the field proves that they are not so. 



(2) Certain kiyids of mineral constituents are almost sure to 

 make a massive Tnetamorphic rock when the process of met amor - 

 phism is one attended with much heat. — Hornblende and augite 

 are minerals of this kind. Both are rather fusible, and crystal- 

 lize readily, so that heat easily obliterates all traces of bedding. 

 This principle alone will account for the fact that the rocks north- 

 east of Bernardston, alluded to above, are massive wherever horn- 

 blende is the chief ingredient. It explains also the existence of 

 the massive labradorite-dioryte among the schists west of New 

 Haven. Feldspar also, when alone, oi' accompanied by quartz 

 without any associated mica (as in felsyte, quartz-felsyte, granu- 

 lyte), is almost sure, under the circumstances mentioned, to make 

 a rock, with the bedding obliterated, in other words, a massive 

 rock ; and only with a low degree of heat in the metamorphism, 

 would any original bedding be retained. And even if hornblende 

 is present, there is the same tendency to massive forms. Serpen- 

 tine is another species that makes almost necessarily u massive 

 rock, whatever the method of origin, because the mineral has 

 nothing in its structure that favors any other condition. 



(3.) Pressure may he a source of schistosity or foliation ^ and 

 it may also obliterate bedding. — On the first of these points 

 illustration is not necessary. As to the second, there are many 

 examples in the crystalline limestone region of Western New 

 Endand, both in Vermont, Massachusetts and Connecticut. At 

 West Rutland, Vermont, as first observed by Prof. Edward Hitch- 

 cock, many limestone beds have been cemented by the pressure 

 which gave them their high dip into a bed of great thickness, so 

 that masses as large as a moderate-sized house could be cut out 

 if needed. The component beds are easily distinguished in the 

 southernmost of the three quarries. Moreover, in the middle of 

 the same valley the metamorphism of the limestone stratum was 

 not complete enough to obliterate the fossils — shells, corals and 

 crinoids beini' distinguishable ; so that there could have been no 

 fusion to produce the coalescence. As this welding of beds is so 

 perfect in the limestone, it is reasonable to believe that a similar 

 cause may have acted in the case of feldspathic, hornblendic and 

 auo-itic rocks, without even the aid of incipient fusion. 



