OF DENISON UNIVERSITY. 5 



The fluctuations and arrangement accompaning the formation 

 of the lower Helderberg strata in eastern New York, show that the 

 upward movement begun there at the close of the Cambrian period, 

 still further progressed after the deposition of the Hudson group, 

 throwing the rocks of that formation above the level of the ocean into 

 anticlinal and synclinal folds east of the Hudson, while decreasing in 

 intensity westward. The Hudson formation may have furnished sed- 

 iment from which the Oneida comglomerate was in part derived, but 

 it is apparent that the later beds of the Niagara period had a connect- 

 ion with the vastly thicker formation in Canada through a channel 

 possibly leading northeastward from western New York. With only 

 a thickness of 300 to 400 feet in Ontario, increasing to 1,300 feet in 

 Nova Scotia, it seems possible that the sediment was derived from re- 

 gions north or northeast of New England, while the intimate relation 

 of its fauna to that of England point to a very close biological relation- 

 ship between the two areas, which oftentimes results from an uniform- 

 ity of physical environments. The thinning out westward of the lower 

 Helderberg group in New York, together with its comparative thinness 

 in Tennessee, demonstrates it to be an essentially eastern formation. 

 Unlike the Niagara, however, it thins out very rapidly to the westward 

 until in Cayuga county it has almost entirely disappeared. It is obvi- 

 ous, however, to the most casual observer, that the Helderberg escarp- 

 ment in Albany county must have had a much greater extension north- 

 ward than at present, and after H. Fletcher's determination of the 

 thickness in Nova Scotia (1,000 feet), we can probably admit the 

 truth of Logan's determination that it was connected with the Cana- 

 dian basin through the Champlain valley ; bounded on the east and 

 west by the folds of the Cambrian and the Adirondack range. 



Continuing upward in the geological formations we find the 

 Hamilton group with a thickness of 1,200 feet in the Catskill region, 

 but rapidly thinning to the westward, until in western New York it is 

 scarcely 200 feet thick, while at the falls of the Ohio the beds include 

 20 feet of impure limestone. In eastern Pennsylvania the greatest 

 maximum thickness is 5000 feet, in the Gaspe region 6000 feet. The 

 associations of the specimens I have seen from Perry (?) Maine would 

 indicate an estuary connection with the Gaspe fauna, outside of the 

 main line of deposition. The manner of preservation is very similar 

 to specimens from western New York. It is impossible not to believe 

 that the Hamilton strata did not extend farther eastward, northward, 



