THE HAMILTON ASSOCIATION. 1 39 



cataract are also retreating in some places, not so much from the river 

 undermining the banks, although perhaps, at some points such was 

 the agent, but chiefly from the expansive power of the frost during the 

 winter season, which is sufficient to rend asunder and disintegrate 

 the face of the hardest layers exposed to its influence. You may 

 notice at the upper reservoir, every year, what a vast amount of 

 loosened material has to be carted away when the frost disappears. 

 It must be admitted we committed a grave error in not taking a 

 chisel or two and a heavy hammer with us. Had we been provided 

 with them we could have added a considerable number of much 

 better specimens to our collection of stromatopors, strange fossils, 

 to which Mr. Walker recently called your attention, whose classifi- 

 cation remains as yet undetermined. 



Dr. Spencer, who has studied the Field Geology of the Ni- 

 agara District most carefully alleges the Falls commenced their his- 

 tory when the lake level of Ontario was 138 feet higher than at 

 present, the predecessor of the modern body of water he calls Lake 

 Iroquois. I consider his conclusion quite correct regarding its ex- 

 istence since the glacial period ; but I believe the vast inland sea> 

 fresh water, he has named Lake Warren, existed before the great 

 Ice Age. Could any quantity of lake ice have scored and polished 

 with such regularity the glacial markings we see every where for 

 miles around us, or deposited moraines of the dimensions we meet 

 with on the brow of the mountain ? 



