336 GEOLOGY OF THE SECOND DISTRICT. 



St. Lawrence county, though so well watered by living streams, has few lakes, in conse 

 quence of not extending as far east as the table land upon which they are so numerous. 

 Black lake is the largest and most important ; it is twenty miles long ; and as Indian river 

 empties into it, it may be made a medium of travel or navigation still farther. Its shores are 

 low, and so far as scenery is concerned, it is not likely to be celebrated or praised. 



The Gre.\.t Geological Divisions of St. Lawrence. 



For all useful purposes, and also for accuracy, it will only be necessary to divide this county 

 into three principal regions : 1, The Primary region, comprehending hypersthene rock, gra- 

 nite, gneiss and primary limestone ; 2, Sandstone region ; and 3, Limestone region. The 

 particular kind of sandstone and limestone will be stated in the proper place. 



The first region or division comprcliends more than one-half, but less than two-thirds, of 

 the county. In general, I may say that all that part east of Canton is primary. But to be 

 more precise in these boundaries, as they are few, and may be given with some degree of 

 exactitude, I will commence at the extreme south, and proceed northeast. The primary extends 

 over to the west side of Black lake, but only upon an average seventy or eighty rods, form- 

 ing a narrow belt upon that side of the lake. It crosses two miles north of Depeyster, and 

 runs nearly through the centre of the town towards Canton, running east two or three miles 

 of the natural canal. From Canton, the line of junction between the primary and transition 

 pursues an undulating course, running three or four miles east of Potsdam ; the primary, 

 however, appears at the village, thence to Parishville, and onward to Hopkinton. The line 

 of junction, though it is described as pursuing generally a direct course, still it is more or 

 less undulating the whole distance, varying on either side two or tliree miles. The course I 

 have given, therefore, is what it purports to be ; the general direction being sufficiently accu- 

 rate and correct for all useful purposes. 



I have now given the boundary line between the primary and potsdam sandstone. What 

 remains is to make a similar line of demarkation between the latter and the limestone region, 

 or that which is underlaid by the calciferous sandrock of Eaton. 



Commencing as before at the extreme southern portion of the county, a few miles south of 

 Morristown, the line runs nearly parallel with the St. Lawrence river, crossing the Oswe- 

 gatchie four miles east of Ogdensburgh ; it then diverges to the east, and adheres to that 

 direction until it crosses the De Grasse river two miles east of Columbia, when it runs again 

 about parallel with the St. Lawrence to Norfolk, whence it still pursues nearly the same 

 direction to Brasher and Hogansburgh in Franklin county. 



These lines of demarkation divide the county into three great regions in which the physical 

 geography differs, and also into three distinct geological formations. They are unequal as to 

 size, as has been remarked, but still we may consider the county as divided into three zones 

 or belts ; the eastern, central, and western. All of the first is entirely primary ; all of the 

 central, potsdam sandstone ; and all of the western, which lies along the St. Lawrence, is 

 composed of the calciferous sandrock of Eaton. 



