Birth of Lake Ontario. 449 



to 65 or 70 feet at the western end of the lake. Behind the 

 modern bars and beaches, the water of Irondiquois Bay (a 

 narrow river-like channel) is 78 feet deep ; the Niagara River, 

 72 feet ; and Burlington Bay, 78 feet. These conditions indi- 

 cate that the lake covering these channels was at one time 

 withdrawn, leaving only a few feet of water in the rivers 

 which flowed through the otherwise dry valleys. Here, then, 

 in front of the bays, submerged or buried by more recent accu- 

 mulations (upon re-submergence), is the position of this lower 

 beach extending westward of Oswego, which was formed at a 

 level now 70 feet below the surface of the western end of the 

 lake. Indeed, the uniformly narrow Burlington Beach (b, fig. 

 2), with a length of five miles across the end of Lake Ontario, 

 is thus easily explained as having originated as a small barrier, 

 in front of the shallow river, flowing down the Dundas valley 

 and across the now submerged floor of Burlington Bay. With 

 the more recent backing of the waters of the lake, this bar 

 grew to the proportions of the modern beach, built out of 

 materials derived from the older shores and not from river 

 deposits. 



-At the time when this young beach — now beneath the lake 

 — was being formed, the waters had receded for only from 

 three to five miles from what are now the western shores of 

 Ontario, but they extended farther landward than at present 

 upon its northern side, as shown by the raised beaches, and by 

 the absence of submerged channels. 



The Niagara River was about three miles longer than now, 

 cutting its way over a projecting point of shaly rocks. But 

 this channel is at present filled, and is again further submerged 

 beneath the lake. 



During the continued rise, the waters of the Ontario basin 

 may have been even somewhat further shrunken at its western 

 end, and the waves may have moulded some of the submerged 

 escarpments upon the southern side. The waters upon the 

 southern side could have nowhere been more than about 200 

 feet below the present level, even if that amount of shrinkage, 

 which represents most of the barrier holding the basin above 

 the sea, ever obtained. However, no important geographical 

 event is recorded in any of the possible coast-lines submerged 

 at levels below that just described. 



With the regional uplift, the barrier across the St. Lawrence 

 valley eventually cut off free communication with the sea, at a 

 common level. This uplift has continued until the Iroquois 

 Beach now rests at 972 feet above the sea at Fine, and the 

 modern lake at 247 feet. Thus the modem lake had its birth. 

 This warping at the northeastern end of the lake, during the 

 later and since the Pleistocene period, has been enough not 



