88 F\ REPORT OF PROGRESS. E. W. CLAYPOLE. 



along at least a part of its course it is marked by a line of 

 strong springs. So evident is it when the structure of the 

 county is understood that a man can stand with one foot on 

 the Chemung shales and the other on the Lower Helderberg 

 limestone. 



In estimating the throw of this fault it must be remem- 

 bered that it is not every where of the same extent. At its 

 greatest the olive shales of No. VIII, the Chemung, are 

 brought into contact with the limestone of No. VI, the 

 Lower Helderberg. If we then calculate the throw where 

 it is greatest we shall get the following results. The part 

 of the Chemung appearing at the surface at the fault is as 

 near as I can ascertain about 1800 feet above the base of that 

 group. 



Partial thickness of Chemung, (lower portion,) . . . 1800 feet. 



Total " Portage, 200 " 



11 " Genessee shale, 200 " 



" " Hamilton Upper shale, 300 " 



" " Hamilton sandstone, 600 " . 



»« " Lower Hamilton shale, 500 " 



" " Marcellus black shale, ... 100 " 



" " " limestone and shale, . . 100 " 



" " Oriskany sandstone, 25 " 



Partial " Lower Helderberg limestone and 



shale, 250 " 



Total thickness of rocks thrown by the fault, 4075 " 



Thus within certain small limits of error is the amount 

 of throw calculated at right angles to the bedding. The 

 total dislocation is however much greater. The tangential 

 or horizontal thrust, to which is due the folding of the Ap- 

 palachian strata and their accompanying or. subsequent 

 fracture, forced the rocks on the southeast side of the fault 

 over those on the northwest side along a slope whose angle 

 cannot be determined. It has been represented in the sec- 

 tion as 45° but was probably less. If the amount above 

 given be now increased in the proportion of the sine of this 

 angle to the radius, or multiplied by 1.4, we obtain as the 

 actual displacement of the strata, at this part of the fault, 

 about 5700 feet. 



The Half Falls fault. 



This fault is apparently confined almost wholly to the 



