1893.] NEW YOKK ACADEMY OF SCIENCES. 107 



third of the rock mass, vary in diameter from one-quarter of an 

 inch to two feet, are decidedly angular, and are scattered 

 through the limestone in the most irregular manner possible. 

 At first glance they might be taken for abundant inclusions in 

 a light colored igneous rock, and it is strange that Emmons did 

 not mention the occurrence in support of his theory of the 

 igneous origin of limestone. Examination of other outcrops 

 of a similar nature shows that the schist fragments are the 

 remains of once continuous sheets, either interbedded with or 

 intruded into the limestone, which have been completely shat- 

 tered in the course of metamorphism. Between extreme cases, 

 like that described, and those where the schist is but slightly 

 distorted, there is every possible stage. The schistose layers 

 pass from gentle folds into the most elaborate contortions, in 

 these the schists are often stretched apart, their edges on each 

 side of the break being drawn out to thin wedge shape, some- 

 times with a few flattened lenses partially connecting them. 

 Complete obliteration of the original continuity is rather excep- 

 tional. A peculiar feature of this distortion and fracturing, is 

 that the limestone shows almost no tiace of it. It has the 

 ajDpearance of a plastic mass in which the schists could move 

 with considerable freedom. The conspicuous result of meta- 

 morphism in the limestone is crystallization, and this has 

 obscured the mechanical effects. 



The true character of the schistose rocks is often greatly 

 obscured by this contortion, with the accompanying mineralogi- 

 cal changes ; and it is sometimes very diflScult, or even 

 impossible, to decide whether they are interbedded strata or 

 intrusive sheets. The smaller masses of pegmatite have been 

 much shattered, and are often reduced to small lumps of quartz 

 and feldspar, scattered throvigh the limestone. But so lar as 

 observed, the pegmatite yields to strain only by fracturing, and 

 never shows the j^reliminary contortion that is so general in the 

 schistose layers. 



Date of Metamorphism. — A comparison of the different forma- 

 tions serves to fix the time of metamorphism only in the most 

 general way. It leads to the conclusion that the most intense 

 metamorphism, which produced such marked changes in the 

 limestone and associated rocks, occurred before upper 

 Cambrian time. A second stage of metamorphism is recorded 

 in the sandstone, and must therefore belong to post-Potsdani 

 time. 



In conclusion, it may be added that the writer hopes to do 

 further work in the neighborhood of Gouverneur, as well as in 



