2 
MUSEUM BULLETIN NO. 23. 
1895, attention was again directed by Gilbert 1 to the Trent 
Valley outlet channel. Gilbert found evidence of powerful 
stream action at various places along the Trent valley. He noted 
that, between Stony lake and Rice lake the outflow was divided 
between the Indian River and Otonabee River valleys and that a 
delta, apparently formed by the Algonquin river, was deposited 
in Rice Lake basin at a height corresponding to the calculated 
position of the Iroquois water-plane, but also corresponding to the 
plane of Rice lake. He found also that the outlet channel does 
not stop at Rice lake but "continues with undiminished strength” 
down Trent River valley to the present level of Lake Ontario at 
Trenton. Gilbert pointed out that this indicated that the 
Algonquin river continued to flow long after the disappearance of 
Lake Iroquois. In 1893 Taylor had also examined the Trent 
Valley outlet channel and made the same observations that 
Gilbert did "except that the channel near Trenton seemed to 
him somewhat smaller and less capacious than that at Fenelon 
Falls and less thoroughly scoured; this, however, may be an 
error.” 2 In 1903, Coleman 8 examined and mapped the Iroquois 
beach in Ontario. He showed that a delta apparently formed 
by the Algonquin river at Peterborough was deposited in a small 
lake, which he named Lake Peterborough. He considered that 
this lake was formed in a restricted valley tributary to Lake 
Iroquois. He found that the altitude of Lake Peterborough was 
somewhat higher than that of Lake Iroquois but no serious doubt 
was cast upon the correlative relation of the two lakes. More 
recently Goldthwait 4 has inferred from a comparison of the 
amount of uplift as shown by the warped water-planes of Lake 
Algonquin and Lake Iroquois that the two lakes must have been 
nearly contemporaneous, for both water-planes have apparently 
been upwarped by the same set of epeirogenic movements and 
the water-plane of Lake Iroquois shows very little greater defor- 
mation than that of Lake Algonquin. 
i Gilbert, G. K., “The Algonquin river” (Abstract). Am. GeoL, vol. 18, 1896, p. 231. 
s U. S. Geol. Surv., Mono. LIII, p. 444. 
* Coleman, A. P„ “The Iroquois beach in Ontario”, Bull. Geol. Soc. Am., vol. IS, 1903, 
pp. 357-3S8. 
4 Goldthwait, J. W., “Isobases of the Algonquin and Iroquois beaches, and their signifi 
cance”. Bull. Geol. Soc. Am., vol. 22, 1910, pp. 227-248. 
