LAKE ALGONQUIN. 
13 
RELATION OF LAKE ALGONQUIN TO LAKE IROQUOIS. 
It is evident that the delta in Rice lake at the mouth of 
Indian River valley was not formed by the present stream but 
must have been formed by the Algonquin river. The question 
arises whether the water body in which it was deposited was Lake 
Iroquois or a lake which existed in Rice Lake basin after the 
disappearance of Lake Iroquois. This question can be answered 
by an examination of the altitudes of the Iroquois shore-line in 
Rice Lake and Campbellford districts. 
The altitude of the highest Iroquois beach near Healey 
falls, 5 miles north of Campbellford, was determined by the 
writer, by levelling from a bench-mark established at Healey 
falls. The altitude of the highest strong gravel beach ridge 
was found to be 689 feet. A lower strong beach occurs at 679 
feet. These altitudes confirm Coleman’s determination of the 
altitudes of Iroquois beaches at this point. 1 On the north side of 
Rice lake, 3 % miles eastof the mouth of Indian river, a well marked 
beach, which is probably the highest Iroquois beach, occurs at 
62 1 feet. A strong shore cutting slightly above the present level 
of Rice lake also occurs near the mouth of Indian river. The 
trend of the isobases of Lake Iroquois, assuming for this district 
the direction of tilt north 20 degrees east as determined by Cole- 
man, 2 also indicates that the Iroquois water-plane would coin- 
cide with the plane of Rice lake not far west of the mouth of 
Indian river. Rice lake owes its present existence to drowning 
of a large valley by uplift of the outlet. The lake could not have 
existed previous to the uplift which is shown to have taken place 
by the deformation of the Iroquois beach, unless the water body 
which occupied Rice Lake basin was an embayment of Lake 
Iroquois. The delta was formed before uplift took place. Hence 
it seems evident that the delta at the mouth of Indian river 
is to be correlated with Algonquin river and Lake Iroquois and 
it follows that Lake Iroquois was for a time at least, contempo- 
raneous with an early stage of Lake Algonquin. 
The continuance of a strongly marked outlet channel along 
Trent river below Rice lake and extending as far as Trenton on 
1 Coleman, A. P., “The Iroquois beach in Ontario," Bull. Geol. Soc. Am., yqI. 15, 1903. 
* Loc. cit., dp- 359-363. 
