212 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY, 



Saxicava rugosa, and Mytilus edulis, and at the bottom the bones of 

 a Cetacean associated with S. rugosa and a Nucula or, more probably, 

 Leda. The Leda-clay of Dr. Dawson, at Montreal, is also about 120 

 feet above the river, or 140 feet above the level of the sea. If the 

 so-called " Nucula' ' of Lake Champlain be Leda Portlandica, the 

 Montreal beds contain the same assemblage of fossils (except San^ 

 guinolaria fusca). In the Montreal beds Sir Wm. Logan also found 

 a number of the caudal vertebrae of a Cetacean. The beds at Green's 

 Creek, Ottawa, containing the same assemblage of shells, Mallotus 

 villosus, and remains of Seals, are 118 feet above Lake St. Peter, 

 and 140-150 feet above the sea. Marine shells {Saocicava rugosa, 

 Mya, Mytilus edulis, and Tellina Oroenlandica) occur at Kingston, 

 at the entrance to Lake Ontario. Dr. Dawson shows good reason 

 why the above-named fossiliferous deposits on the St. Lawrence 

 and Ottawa should be considered equivalents. In addition, I am 

 of opinion that this conclusion may be extended to the Kingston 

 beds, and that the beds of Lake Champlain leading down to those 

 of the Hudson are of the same date ; and if so, then I cannot doubt 

 that the laminated clay that overlies the older boulder- drift of 

 the Hudson Yalley is a larger development of the same formation, 

 the whole having been deposited at the close of the drift-period. In 

 that case, a long marine strait filled the vaUey of the Hudson, and 

 communicated with the sea that, according to Dr. Dawson, then occu- 

 pied the whole of Lower Canada south of the Laurentine Chain, and, 

 stretching westward, covered the area of Lake Ontario, and washed 

 the great Niagara escarpment which formed its southern coast. 



Probable date of the origin of Niagara Falls. — It has been shown 

 by Mr. Hall and Sir Charles Lyell, that when the Niagara escarpment 

 rose above the water, the Falls of Niagara began by the drainage 

 of the upper lake -area falling into the sea over the edge of the 

 escarpment above Queenstown and Lewistown. It is not impro- 

 bable that Lake Erie extended at that period much further towards 

 the present Falls ; and, agreeing in the general conclusions of these 

 observers and of Dawson, it follows that, if the sea of the Leda-clay 

 washed the base of the escarpment, the Falls of Niagara commenced 

 during the deposition of that clay, or a little before the close of the 

 drift-j[>eriod* . If, with accumulated data, the rate of the past re- 

 cession of the Falls be actually determinable, we shall then be in a 

 condition approximately to show the actual number of years that 

 have elapsed since the close of the North American drift. It may 

 perhaps appear that the approximate period of 35,000 years, given 

 by Sir Charles Lyell for the erosion of the gorge, is below the reality. 



Drift and other Late Tertiary deposits at Niagara. — I have little 



* It is well known that the Niagara escarpment is of older date than the drift. 

 Lake Erie is 329 feet above Lake Ontario ; and the older boulder-drift Hes indif- 

 ferently on the lower plain and on the table-land. No one has yet attempted to 

 show at what period this old coast-cliff, about 400 miles in length, was formed. 

 The upper platform, on a grand scale, bears the same physical relation to the 

 rocks of Lake Ontario that the Oolitic escarpment and table-land in England 

 does to the Lias and plains of New Red Marl below. 



