398 GEOLOGY OF THE SECOND DISTRICT. 



This rock is very fragile, and never sufficiently firm for roofing slate. It decomposes 

 rapidly, and hence the surface which it underlies is always rounded or rolling. When mois- 

 tened or wetted after removal from the bed, it breaks or cracks to pieces ; and hence, we find 

 that wherever streams pass over this rock, they invariably cut deeply into it, and form gorges. 

 It is more owing to this cause that the streams produce so much effect in forming channels in 

 the rock, than to their mechanical action. For we find the rock constantly breaking down 

 simply by drying after a rain ; and especially by the absorption of water between its layers, 

 and subsequently freezing, the mass is still more rapidly broke down into earth or an argilla- 

 ceous soil. 



The color of this rock is black, but by exposure the outside becomes grey. The mass is 

 essentially argillaceous, and rarely if ever shaly or sandy. It differs in this particular from 

 the argillaceous strata of Loraine. It has natural joints, or rather a crystalline structure, • 

 where the strata are the firmest and hardest. The inclinations of the edges of the principal 

 joints to each other, are 60° and 120° respectively. Other lines divide the mass, but they 

 are subordinate to these. The dip of the rock is southwest : the angle is, however, very 

 moderate or gentle ; and, unless locally disturbed, it never exceeds five degrees. 



In order to examine the utica slate in this county, the route which may be pursued is to 

 take the road from Adams to Tylerville. On this road, one mile from Adams, the slate appears 

 in the south bank of the creek, and the trenton limestone on the opposite side. This is a 

 point of some interest, for there is a shght disturbance of the rocks, and the trenton is appa- 

 rently raised to a level with the slate. The dip of the limestone is west, and its inclination is 

 four degrees in that direction. The fractured edge trends northeast, in a low ridge not 

 exceeding twenty or thirty feet. The south side is underlaid by the slate, though much con- 

 cealed by soil and drift. At different points upon this road, wherever the creek is examined, 

 we usually find the limestone in its bed, and the slate at no great distance in the banks. 

 Natural joints of the limestone on this route, N. 45° E. ; at five miles from Adams, they are 

 S. 75° E. ; dip southwest. Natural joints of the slate, N. 45° E. The slate is entirely 

 conformable to the limestone on which it rests. 



The slate of the gulfs or ravines is frequently in a state of perfect decomposition, lying in 

 mass on the banks, and sometimes in powder hke a pile of ashes. This result has been pro- 

 duced by the dissemination of sulphuret of iron. The taste of this decomposed mass is 

 slightly styptic, but indicates only a small proportion of the sulphate of iron. The cliff under- 

 laid by this material is of course constantly falling down, being undermined by the washing out 

 of the slate by rains, and by its own imperfect coherent state. It is not improbable but that 

 this mass of decomposing slate might be converted into alum, by pursuing with it the usual 

 method. An experiment could be tried at a small expense, and the material is so abundant 

 and accessible that it certainly deserves some attention by those who own the soil. 



A very large proportion of the slate, wherever it is exposed, exhales a strong bituminous 

 odor on being struck or broken ; and frequently, in the fracture of a large mass, the odor may 

 be perceived twenty feet distant. 



