2'= 



5' 



7" 



' I0"= 



3' 



7" 



6"= 



I' 



9" 



6"= 



I' 



3" 



9"= 



9" 





LOWER SILURIAN SYSTEM OF EASTERN MONTGOMERY CO. 433 



A^ Massive or weathering to thin irregular 

 layers. Dark drab; contains corals (Strepte- 

 1 a s m a). 



A^ Thin distinct layers at base but seeming to 

 coalesce above into thicker layers ; dark drab. 



A* Grayish blue, very smooth, compact lime- 

 stone. 



A^ Thin layers of light drab blue limestone. 



A2 Compact drab blue with smooth joint faces. 

 Birdseye. 



A^ Thin layers of arenaceous limestone to 

 river level. Calciferous. 



The above section affords an excellent opportunity to study the 

 lithologic characters, color and weathering of the lower divisions 

 of the Trenton stage. The layers are under water at the flooding of 

 the Mohawk river and are thus freed from soil stains so that they 

 clearly show the normal weathering of the rock. The difference in 

 color between the massive Trenton and Black river and Birdseye 

 beds (A2-8) is very conspicuous and the line between the Black 

 river and Trenton is sharp. The line between the Black river and 

 Birdseye substages is not so distinct but may probably be drawn 

 at the top of A^. The Birdseye is very variable in thickness through- 

 out this region. 



Above the section just described the Trenton limestone is ex- 

 posed at several places in the lower part of Amsterdam west of 

 the Chuctanunda creek, and specially in the northwestern part of 

 the city at an altitude of 90 feet above river level. The layers 

 exposed at the latter point are highly fossiliferous and dip strongly 

 to the south and west. They belong to the lower part of the 

 Trenton substage. Along Spring street in the western part of the 

 city the Trenton thins out, and at one or two points the Calciferous 

 is again exposed. At the head of one of the streets crossing Spring 

 street about a mile west of the Chuctanunda is a small quarry 

 recently opened. In this quarry a three foot layer of Birdseye lime- 

 stone of excellent quality for construction stone is worked. The 

 stratum of Birdseye rests on very arenaceous limestone and is 

 capped by a few feet of extremely lumpy, black, somewhat fossilifer- 

 ous limestone. Not far west of this point the Calciferous is again 

 exposed and extends up the bed of the creek half way between 



