pyroorystalline limestone. 
lower Silurian rocks. Upon lake Champlain the evidence of 
movements of a much later date are fully established. The 
fact that these movements have taken place since the drift, was 
made known long ago in the reports of the New York survey. 
It can not he determined whether they extended to the central 
mass of mountainsj situated between lake Champlain and the 
St. Lawrence. All that portion however of the hypersthene 
rock which extends to the lake has been raised about five 
hundred feet since the drift period. 
PYROCRYSTALLlNE LIMESTONE. 
§ 64. Primary limestone—metamorphic limestone in part. 
There can be no doubt that limestone occurs among the most 
ancient consolidated rocks of the globe. The investigations 
which I made sixteen years ago satisfied me on this point. At 
that time no one had entertained this view in this country.* 
The rock is coarsely crystalline, usually white, or gray, or 
greenish, rarely blue. It occurs in beds beneath granite, and 
Fig. 6. 
frequently underlies and penetrates it as in fig. 6: a limestone^ 
b granite. The locality where it may be observed beneath 
granite is one and a half or two miles south of Clintonville, 
* New York Geological Report for 1838, for the northern district. 
