182 ERIE DIVISION. 



cropping slopes are often concenlod liy a tliick mantle of its own debris. It forms the 

 upper terraces in Schoharie, Carlisle, Cherryvaliey, Springfield, Waterville on the road to 

 Cassville, Madison and Manlius (wliere the highest hills are crowned with the Marcellus 

 shales), Onondaga and Camillus, shores of Cayuga lake above Springport, at Aurora in. 

 Seneca county (a little distance south of Waterloo), on Flint creek two miles south of 

 Vienna, at tlie outlet of Concsus lake, two miles south of the village of Caledonia, and on 

 Allen's creek at Leroy. Still fartlier, and west of Leroy, at Alden, the upper part of the 

 rock is exposed ; but generally in this part of the State, the deep beds of drift and debris 

 effectually conceal this rock from observation. 



The southeastern exposure of the Marcellus shale, from the northern slope of the Hel- 

 derberg to Ulster county, furnishes but few localities of much interest. Upon the hills, or 

 rather low mountains west of Leeds or Catskill, Saugerties and Kingston, this rock occupies 

 the first distinct terrace, Init the debris conceals the strata too much to permit us to observe 

 the connections or the fossils. 



Septaria. The Marcellus slate is the first rock which contains those concretionary bodies 

 known as septaria. These oval and sometimes round bodies are impure limestones, the 

 materials of which v.'ere deposited along with the shaly matter ; but in consequence of the 

 play of aflSnities, the calcareous part separated from the great mass of shaly matter, and 

 the molecules combined to form the bodies under consideration. During the process of 

 drying, the argillo-calcareous matter shrinks and cracks, forming thereby septa which 

 radiate from the centre and terminate in the circumference : these are subsequently filled 

 by infiltration, either of calcite or the sulphate of barytes or strontian. In the formation 

 of septaria, we are furnished with a beautiful as well as a striking illustration of a series 

 of molecular changes, which the strata may and do undergo during the process of soli- 

 dification ; and indeed we may be well assured that even the solid strata are continually 

 undergoing extensive changes, in consequence of the ever active and energetic forces with 

 which matter is endowed. Hence it is important, in speculating upon the conditions 

 of strata, to bear in mind tiie fact that matter is never quiescent; never reaches that dead 

 point where it is destined to remain stationary. Freedom of motion is found in fluids : in 

 the tenacious clays, the particles are freer than in the granite of the mountains ; but even 

 here they feel the force of molecular attraction, which results in regularity though not in 

 stability of form ; for heat and cold must continually modify the shape of the particles, by 

 altering the saliency of their angles. 



Limestone stratmn associated vnth the Marcellus slate. At Schoharie, Cherryvaliey and 

 Manlius, a black limestone, from five to ten feet in thickness, occupies a position in the 

 midst of the shales. It is an argillo-calcareous rock, and probably is capable of forming an 

 excellent hydraulic mortar. It weathers out into extremely rough masses, so that persons 

 who have occasion to work the rock generally call it chawed rock. In the Hclderberg, this 

 mass is concealed ])y debris, if it exists there ; and it is not distinctly recognized in the 

 western counties. The composition of this limestone does not differ materially from that 



