308 Review of the New York Geological Reports. 



geological formation. Thus have been produced the upper fall 

 at Rochester, the falls at Wolcott and at Shelby ville. 



The shale is more constant in its thickness than the limestone. 

 The former varies from eighty to one hundred feet ; the latter is 

 only thirty to forty feet in Wayne County ; seventy to eighty feet 

 at Rochester, and one hundred and sixty four feet at Niagara Falls. 



The Niagara group as well as the Hamilton group, are both 

 colored light blue on the geological chart, but the former is a 

 shade darker and lies further north, and comprises a narrower, 

 wedge-shaped tract of country, south of and parallel to the Clin- 

 ton formation ; broadest in the west at the Niagara River, and 

 running out in the east in Litchfield tov/nship near the corner 

 of Herkimer and Oneida counties, so that its eastern termination 

 falls a little west of the preceding group. 



At the outcrop of the shale and underlying the Medina sand- 

 stone, the clay of the former and sandy products of the latter 

 afford a soil of wonderful fertility, admirably adapted to the 

 growth of wheat ; sometimes however the clay predominates, 

 and then the soil is too stiff and retentive. The soil over the 

 limestone is for the most part loamy, with a rapid drainage 

 through the fissures of the limestone rock. 



Though there is some variety of minerals in this formation, 

 none are found in sufB.cient quantity to be of much economical 

 value. The shale affords in sheltered situations, sulphate of mag- 

 nesia, sulphate of alumina, muriate of soda. Nodules of gypsum 

 are also found replacing organic substances. Iron pyrites is very 

 common throughout the shale and occurs also in the limestone, 

 and near their junction some green carbonate of copper has been 

 found. The limestone has yielded some fine specimens of cal- 

 careous spar crystallized in scalene dodecahedrons ; also pearl 

 spar, brown spar, selenite, sulphate of strontian, anhydrite, and 

 occasionally fluor spar, blende and galena. The latter in some 

 situations appears to be distributed in minute veins in the calca- 

 reous beds : during the excavations for the Erie Canal at Roches- 

 ter, several hundred pounds of sulphuret of lead were found in 

 one cavity. 



Penetrating the calcareous spar lining imbedded geodes, are 

 long prismatic hair-like crystals, which Dr. Beck regards as ach- 

 mite. At the Cold Spring quarries two miles south of Lockport, 

 in cavities of encrinital layers, native sulphur is not uncommon. 



