342 Dr. Bigsby's Sketch of the Topography 



rock. It is a thin stratum, but continuous for 200 to 300 miles. 

 It is four feet thick at Genesee Falls, eight feet at Niagara 

 River, twelve feet on the creek east of Lockport, and fifteen 

 feet at most places, where it crops out with the saliferous rock, 

 near the Mohawk. It varies considerably, however, in its tex- 

 ture and its constituents. In some places it seems to be con- 

 siderably argillaceous ; in othei's, quartzy ; and in others again, 

 it contains considerable carbonate of lime. — (G. S. p.ll5, 116.) 



Above this grayband are placed conformably two sets of 

 strata abounding in iron ore. The lowest of these Mr. Eaton 

 names 



Ferriferous Slate, describing it as soft, almost homogeneous, 

 argillaceous, greenish-blue and bluish-green ; a bi'ittle, ge- 

 nerally a shaly slate. — (P. 36.) 



This rock is seen frequently in connection with those above 

 and below it : its thickness is valuable. At the Genesee Falls 

 it is twenty-three feet thick, perhaps the average. It is but 

 ten feet thick at the Verona Iron Mines. It runs about two 

 miles and a half south of Lake Ontario, from Irondiquet's 

 Bay to Sodus Bay. The iron ore is mostly the argillaceous 

 oxide, sometimes passing into the jaspery variety. The best 

 kind is the lenticular. It being the peroxide of iron com- 

 bined with alumine, the colour is bright red, and it is of a soft 

 texture. Some specimens may be rubbed into a fine powder 

 between the fingers. It has an unctuous feel, and stains the 

 hands deeply and permanently. Though it will generally give 

 but 30 per cent of iron, it is so easily reduced that it is a very 

 profitable ore. " The jaspery variety is hard, and difficult to re- 

 duce. It is not at present used at the furnaces. Sometimes the ore 

 is in a distinct bed or layer between the two ferriferous strata. 

 It is more commonly attached to the upper sui'face of the slate, 

 and intermixed with the layers of sandstone. Sometimes it is 

 embraced between layers in both rocks. In the banks of 

 Genesee River, at the Falls, it appears like a distinct stratum 

 between the two rocks. It has the same appearance in some 

 other places. It is so remarkably continuous, that there would 

 perhaps be no impropriety in calling it a stratum of argilla- 

 ceous iron ore. I have seen it between, and in the adjoining 

 parts of, these rocks, at frequent intervals from near Little Falls 

 to Queenston in Canada, a distance considerably exceeding 

 two hundred miles. It is never wanting in the canal district, 

 where the ferriferous rocks are present. 



" The whole thickness of the iron formation at Genesee 

 Falls is thirty-eight feet. Here the iron ore is but one foot 

 in thickness. In most of the oi'e beds which are wrought, the 

 ore is twelve to twenty inches in thickness. In several loca- 

 lities 



