ST. LAWRENCE COUNTY. 337 



In the primary region, wc find the rocks possess the greatest variety of character and com- 

 plexity in the southern part. In the eastern, at Scriba, Bloomfield, Emilyvillc, Chamont, 

 Sarahsburgh, Chfton, and otlier places, the rocks arc more uniform, and contain less lime 

 than in the region of Rossie, Gouvcrncur, Hammond, and others in the neighborhood. 



The eastern border of the sandstone is broken, and usually thin. Sonic portions of it, as 

 at Potsdam, are finely stratified, form a beautiful building material, and in fact are largely used 

 for this purpose. 



The calcifcrous sandrock is in many places nearly a pure limestone. Tlic lower part, 

 however, is not so fossiliferous as in Clinton ; but at a few localities it furnishes a few fossils, 

 and, as a whole, preserves throughout the character of this rock in other places. It exhibits 

 at several places a large development of the drab-colored layers, which are used at Wadding- 

 ton for a water cement. It furnishes it in great abundance at Hogansburgh, Massena, Nor- 

 folk, and probably wherever this mass is well exposed. It is worthy of remark, that a very 

 large proportion of surface is concealed by drift, both in the sandstone and calcifcrous regions. 



OF THE INDIVIDUAL PRIMARY ROCKS. 



Hypersthene Rock. 



The existence of this mass in the extreme eastern part of this countjr, is well established. 

 I saw boulders of it first high up the Oswegatchie, and afterwards in place in the vicinity of 

 Cranberry lake. Of its extent and its relations, I am unable to speak with much confidence. 

 At the time of my visit, I received the impression that it occurred under the same circum- 

 stances as in Essex ; that it was connected with, or rather embraced, the iron ores of this 

 region ; and that it was, in fact, a prolongation or extension of the Essex mass. I have not, 

 however, been able to confirm these impressions : no opportunity having occurred for visiting 

 again this part of the wilderness of New-York. I shall not, therefore, attempt to give the 

 extent or relations of this rock, being obliged to content myself with the bare mention of its 

 existence in the part of the county already designated. 



Granite. 



At the commencement of this county, I remarked that the structure of St. Lawrence is 

 complicated, so far as the Primary system is concerned. This condition arises from the 

 frequent occurrence of two or three rocks within a small area, without regard to order or 

 system, and also from the passage of the same rocks into each other. As an exemplification 

 of this statement, the reader has only to peruse what was written in the first pages of this 

 report upon the granite and limestone of this county, or to make a personal examination of 

 these rocks in the field. He will find that granite often passes into limestone or gneiss, and 

 vice versa, the limestone and gneiss pass into granite. 



Geol. 2d Dist. 43 



