360 GEOLOGY OF THE SECOND DISTRICT. 



Observation had long since proved that a given mineral substance, occurring in veins, was 

 liable to be unproductive when it deviated from its usual course. It is a matter of some 

 importance to be able to find, in this country, not only the same general arrangements and 

 associations as in Europe, but tlie same leading facts in the distribution of mineral matter. 



LOWER MEMBERS OF THE NEW-YORK SYSTEM. 



I have divided the surface rocks of this county into three classes : the primary, which oc- 

 cupies the whole of the eastern and southeastern parts ; the sandstone, which is nearly 

 central ; and the limestone, which occupies a belt along the St. Lawrence river. A very large 

 proportion of the district occupied by the first class of rocks is still covered with forest, and 

 is only generally known, or it has been particularly examined in only a few places. The other 

 districts are well known, and they are as different in character from the fiistas possible. The 

 only mineral productions arc derived from the first by transports, as the bog iron ores, or else 

 are confined to the rocks themselves. 



Potsdam Sandstone. 



The quarries of this rock at Potsdam are situated upon the De Grasse river, three or four 

 miles southeast of the village. They are sixty or seventy feet thick. The rock at this place 

 is composed of moderately fine particles, and very uniform in size ; hence it is even-bedded ; 

 and what is worthy of remark, is the perfectly smooth and even surfaces which the layers pre- 

 sent. Thin sheets of the rock, twenty-five or thirty feet square, can be raised without diffi- 

 culty. The layers vary in tliickness from one inch and even less, to two feet ; but each wide 

 layer, tliough no distinct seam appears, may be separated into many, so perfectly fissile is the 

 rock. The general color of the mass is yellowish brown, but the tint of each layer differs 

 somewhat from those adjacent to it ; so that the rock, upon the fractured edges, wears a slight- 

 ly striped aspect. 



This quarry furnishes the most valuable stone in the State, being so perfectly workable and 

 manageable, especially when first raised, that few materials for building could compete with it, 

 if situated near a market. As it is, the Potsdam sandstone is largely employed for building 

 in the adjacent towns. It has been transported sixteen miles overland for this purpose. The 

 buildings constructed of this material present a remarkably neat appearance ; and as the rock 

 is free from sulphuret of iron, it does not appear stained and soiled after a few years exposure 

 to the weather. 



In addition to the common purposes of building, tiiis rock is largely employed as a fire- 

 stone ; hence it is used for the hearths of furnaces, for which purpose it is peculiarly well 

 adapted, by reason of its granular structure, and the entire absence of crystalline action. 



The phenomena presented by this rock are rarely of an interesting kind. The stratification 

 is usually quite perfect, though we frequently saw instances of diverse stratification, as in the 

 following diagram : 



