98 NEW YORK STATE MUSEUM 



formations " was written by Ulrich, and the final chapter on 

 oscillations is a joint production. 



The section. The rocks with which this paper is especially 

 concerned are those heretofore classed as Potsdam and Beek- 

 mantown (Calciferous). At Ticonderoga we found the -ordinary 

 Champlain succession of these rocks, Potsdam sandstone, grad- 

 ing up into division A of the Beekmantown through a series of 

 passage beds, and this followed by the other four divisions of 

 the Beekmantown, as established by Brainerd and Seely. The 

 Potsdam is chiefly a vitreous, well cemented, light colored sand- 

 stone, with some weaker beds with calcareous cement in the 

 upper portion. The passage beds consist of alternating beds of 

 vitreous sandstone, calcareous sandstone, and gray dolomites 

 which are usually somewhat sandy. With disappearance of the 

 sandstone beds we pass into division A, chiefly a dolomite forma- 

 tion, largely of dark gray, finely crystalline beds below, running 

 up into more coarsely crystalline, very light gray beds above, 

 which are apt to be full of chert. Though not positive in the 

 matter we are disposed to believe that Brainerd and Seely re- 

 garded the latter as forming the lower portion of their division B. 

 At all events we find an unconformity at their summit wherever 

 we have seen the horizon exposed, and we class them with the 

 darker colored dolomites beneath. Frequent reefs of Cryptozoon, 

 chiefly C. p r o 1 i f e r u m , are found in both the dark and light 

 colored parts of the formation, and the summit is very apt to be 

 formed of a massive, Cryptozoon reef, often heavily silicified. 

 Lying on these in the section we measured at Ticonderoga 

 appear beds which seem to belong to division C. The beds of 

 dove limestone which constitute the most distinctive part of 

 division B at Shoreham, Vt. and elsewhere in the Cham- 

 plain valley are absent in the Ticonderoga section, apparently 

 because of nondeposition. Division C is followed in order by the 

 beds of D and E, and the last by lower Trenton, but the suc- 

 cession is somewhat disturbed by faulting. 



Our section at Whitehall exhibited the Potsdam, passage beds 

 and overlying dolomites, reaching up into the coarse, light col- 

 ored, upper beds, but the summit and the overlying beds were 

 not reached. What was seen was exceedingly like the corres- 

 ponding part of the Ticonderoga section. 



Again at Saratoga the section was quite similar, though with 

 two prominent differences. Instead of the Potsdam grading 



