142 NEW YORK STATE MUSEUM 



of slickensides, this same argument applies against his own hypo- 

 thesis, at least as regards the under sides of the disturbed zones. 

 Thus, when the disturbance took place the limestone layers not only 

 were contorted but were hard and brittle enough often to break 

 sharply and rub over each other with occasional evidence of slicken- 

 sides, and it is quite reasonable to ask why the sliding of large 

 masses of relatively hard rock on the sea bottom took place without 

 leaving distinctly streaked or slickensided gliding surfaces. 



The statement that instead of clearly defined drag (or gliding) 

 surfaces there is often gradual transition between the contorted 

 zones and overlying strata may be answered by saying (a) that the 

 writer's observations show rather sharp separation between the dis- 

 turbed strata and overlying undisturbed strata to be quite the rule 

 (see figure i and accompanying plate) ; and (b) that the few blocks 

 of apparently undisturbed rock within the horizons of the disturbed 

 zones are blocks which either were moved en masse without being 

 crumpled or they are blocks which may have moved relatively little, 

 if any, while the overlying strata slipped along. Blocks of this 

 latter class would have acted as local buttresses against which the 

 deformed layers may have piled up to thicken locally the disturbed 

 zones. Thus, along the footpath just south of the railroad bridge, 

 the strata seem to be in normal order ; then passing southward, there 

 are masses of tilted and broken strata forming a zone of unusual 

 thickness (10 to 15 feet) ; and finally, just opposite the High falls, 

 the highly contorted and broken zone occurs with thickness of 

 5 to 8 at the same horizon. Such an arrangement of masses 

 within the horizon of a contorted zone is quite in harmony with the 

 idea of northwestward differential movements. 



The very local occurrence of the phenomena in proximity to the 

 thrust fault at Prospect and the remarkable coincidence of the 

 strikes of this fault, the distinct folds in the Trenton formation, 

 and the folds and fractures within the contorted zones are facts 

 not to be lightly brushed aside by saying : " Precisely the local 

 occurrence of the phenomenon which 2^Iiller emphasizes appears 

 to me to be out of harmony with his explanation. The cited parallel- 

 ism of the movements is moreover in no sense proof, since to be 

 sure the E. XE-W. S\V, or in general E-\A', direction already gov- 

 erned the Prepaleozoic Adirondack mass, consequently the later 

 movements followed only an inherited character." ^ The present 

 writer fails to see how either the pressures within or the direction of 

 the Prepaleozoic mass in any way whatever argues against the idea 



iHahn: Xeues Jahrbuch, 36:8. 1913. Freely translated from the German. 



