20 



GENERAL OBSERVATIONS. 



GrcqMUe Becl, 

 Vacw Slate. 



only a few hundred sards frniii tl)0 Graptolit.o bods, in areiiapeoiia 

 layers, I found a species of Graptolilc closely rcseinlilin;^ and ]irol)- 

 ably identical with one figured in vol. i, PaUcontology of New York, 

 plate Ti, fig. 1 a, found at Turiu, Lewis County, N. Y., iu the Hudson 

 River group, aud at that time identified with G. pristis, but probably 

 distinct. 



" From the foregoing facts, I infer that the slates below Troy aud 

 in the arsenal-yard, together with the associated metauiorphic lime- 

 stones, are the equivalents of the Trenton limestone ; aud that those 

 at Norman's Kill, which bear the Lewis County sp(;cies of Grapto- 

 lites, are probably a coDtinnati<m of the arenaceous limestones and 

 shales seen iu the ravines anrl railroad cuttings in the town of Knox, 

 Albany County, aud of those layers quarried near Schenectady , N. Y., 

 known as the 'blucstone'; and also that they arc the equivalents ot 

 the Lorraine fhales of Central and North Central New York. All the 

 physical peculiarities of the Hudson Uiver beds, as seen at the locali- 

 ties just mentioned, aro so exactly repeated iu the disturbed and 

 nearly vertical Layers within a few hundred j^ards of the Graptclite 

 beds, that it is difficult to believe they arc not gc"ologically identi- 

 cal. One peculiar feature, often noticed on the rocks at Schenectady 

 and elsewhere, is very common at Normau'sKill : it is the appeaiauce 

 as of flowing mnd si-.ddenly taxed and hardened en the harder layers; 

 the depressions between the folds and wrinkles being filled with fine 

 mud-shale partings, upon which the layers separate with clean sur- 

 faces. 



"The beds at Norman's Kill are so much disturbed and contorted 

 that it is impossible to trace a given layer to any considerable dis- 

 tance. There are also many slight faults of a few inches, or some- 

 times several feet ; but I have seen no evidence of any greater one 

 in the vicinity, neither do I think it probable there is one, or that a 

 proper explanation of the condition of the strata makes it necessary 

 to infer that one exists there. The position of the beds there, and 

 the appearance of the Utica slate and of Trenton limestone in the 

 vicinity, can be more reasonably exi>lained by assuming the presence 

 of a series of folds or overlappiugs, increasing iu strength from the 

 vicinity of the nearly horizontal beds of the Hudson Kiver group 

 only a few miles westward from the river, which thus bring up these 

 lower formations, as shown in the accompanying ideal section. You 

 will find this section similar to one given bj' one of the best and most 

 reliable geologists on page 234, Geological Report of Canada, 1863, 

 for these same formations at another locality. 

 "Vei'y truly, yours, 



"R. P. WHITFIELD. 



"Dr. C. A. White." 



