Becieiv of History of the Great Lakes. — Spencer. 293 
5. Buried Laurentian Valley. Below the outlet of lake 
Ontario, the valley is covered to some extent with drift, but 
the greater part of the barrier closing the lake is rocky. Be- 
tween Georgian bay and lake Ontario, the writer discovered a 
deep buried valley (by a series of borings, for there was no 
superficial evidence of it, although parallel to the Niagara es- 
carpment), beneath the great drift ridges intervening between 
the two waters. The full depth has not been reached, although 
not less than 750 feet beneath the higher ridges, and it is prob- 
ably very much deeper, as indicated by the fjords at both 
ends (in lake Ontario and in Georgian bay) ; so that here is 
the connecting valley between the submerged channels of the 
upper lakes and lake Ontario. The fjords of northern Mich- 
igan and the buried channels continue the evidence that from 
lake Michigan to the outlet of lake Ontario, the ancient Lau- 
rentian river flowed partly through the basins and partl} r 
across the country north of Toronto. The ancient river is 
thus named to distinguish it from the modern St. Lawrence 
river. The connection of the valley of Superior with the Lau- 
rentian river has not been determined; but judging from 
soundings in lake Michigan, we may suppose it to have been 
by way of the northern end of that valley.* 
6. Buried Tributaries. A branch of the Laurentian river, 
now buried beneath 500 feet of drift, extended from the 
southern basin of lake Michigan across the Michigan penin- 
sula and the southern end of the Huron basin. This large 
tributary, which has been named the Huron! an river, is of tin- 
same age as the Laurentian river. 
Through the Erie basin flowed the now buried and sub- 
merged Erigan river. Niagara river was not then in exist- 
ence. But the Erigan passed from the Erie basin across the 
province of Ontario to the great canyon at the head of lake 
Ontario, thus descending to the lower basin. 
Many branches and smaller tributaries are known to have 
joined these greater rivers, as revealed by the borings. In 
some cases there were no changes in the direction of the an- 
cient and modern drainage. In other cases the streams have 
Locally left tin; original waterways and again returned to the 
*"Origin of the Basins of the Greal Lakes," cited before; also "Dis- 
covery of the Preglacial Outlcl of the Basin of Lake Erie into Lake 
Ontario." by tin- writer, Proc Am. Phil. Boc, Philadelphia, 1881. 
