LAKE ALGONQUIN. 
11 
Pigeon lake is 7 feet. The amount of descent in the ancient 
river, as determined from a comparison of the altitudes of the 
correlative beaches in the two basins, was about 6 feet. 
Stony Lake-Rice Lake District. 
From Buckhorn lake to Stony lake the present descent by a 
series of rapids and falls is 39 feet. It is not known what the 
descent in the ancient river was, but it was probably not as great 
as the present fall, for the ancient water-plane was higher than 
the present in these basins. This would have resulted in a 
drowning out of part of the rapids and falls. 
On the south side of Stony lake near Indian River outlet, 
a strong gravel spit, apparently marking a correlative of the 
highest Algonquin beach, occurs at 796 feet. On the south side 
of Stony lake near the entrance to Clear lake a faint gravel beach 
ridge also occurs at 788 feet. 
In Katchiwano Lake basin, southwest of Clear lake, a faint 
shore-line, which is apparently nearly horizontal, occurs at a 
height of 10 feet above the present lake-level. The altitude of 
the water-plane represented by this beach was determined by 
the rock sill at the outlet near Lakefield at a time previous to the 
lowering of the outlet by stream erosion. This beach is not, 
probably, a correlative of the raised beach in Stony Lake basin, 
for it is not similarly deformed. It is also evident that the tilt 
rate of the raised beach in Stony Lake basin is sufficient to carry 
the water-plane below the altitude of the controlling sill at the 
southwestern end of Lake Katchiwano. Hence there was no 
possibility of an outlet from Clear lake and Katchiwano lake by 
way of the Otonabee River valley past Peterborough, at least 
not until uplift had sufficiently progressed to cause an overflow 
by way of the Otonabee River valley. 
Stony lake has at present two outlets, one by way of Indian 
river past Keene to Rice lake, and the other and much the larger 
by way of the Otonabee river through Peterborough to Rice 
lake. During the greater part of the existence of the Trent 
Valley outlet of Lake Algonquin the outlet river from Stony 
Lake basin was by way of the Indian River valley down to 
