128 J. W. SPENCER ON 



composed of limestone derived from older gravel of the hills, or from the rounding of 

 stones washed out by the boulder clay. There is only a small proportion of pebbles of 

 crystalline rocks, although the boulders mostly belong to this class. Along the vï^estern 

 end of the lake from Toronto, and rovind to Niagara River and eastward, the old shore 

 line consisted of bkiils of Hudson River or Medina rocks, only occasionally having any drift- 

 clay upon their flanks. Yet, there, upon the southern side of the lake, all the gravels of the 

 beach have come from the northern side of the lake — the finer material, at least all west 

 of Niagara River, having been transported by coastal currents and ice, and the larger 

 blocks by ice, such as are found every winter upon the present stormy shores. The boulder 

 pavements are here replaced by only occasional erratics of smaller size (having, however, 

 similar relation to the beach) as the source of supply was more distant. At the eastern 

 end of the lake, in New York, the deposits are of similar origin, essentially derived from 

 the drift, or older gravels, upon the Oambro-Siluriau escarpment, which there bounds 

 the valley. 



(8.) Study of the differential elevation of the Beach and the Foci of 

 Uplift. — In order to understand the character of the warping of the earth's crust, it is 

 necessary to ascertain the directions of the axes and the amount of maximum elevation 

 for a vast number of triangles, and calculate the meridianal and oriented equivalents, as 

 the movement has been complicated, and the rate of change variable ; for general resultants 

 covering the Avhole area would be of little value in understanding the terrestrial warpings. 

 Along with triangulations relative to points about Lake Ontario, I have correlated some in 

 the Lake Erie and Georgian Bay regions which bear directly upon the study of Lake 

 Ontario. A few of the most important deductions will be here recorded. 



The eastern equivalent of the uplift, along the southern side of the lake, does not differ 

 in any important degree from its mean value between its western end and Rochester, 

 which is 0.V5 feet per mile. But from Rochester to Oneida Lake, the mean value of the 

 eastern rise is only 0.20 of a foot per mile, and thence a downward movement is indi- 

 cated. 



At the western end of the lake, the maximum elevation' is 2 feet per mile (along an 

 axis N. 28' E.), of which 1.40 foot per mile is the northern equivalent. This amount is 

 increased to 2.5 feet per mile in the region of Toronto. About G-eorgiaii Bay, the meri- 

 dianal uplift amounts to 4 feet per mile. ' To the south-west of the Ontario basin, about 

 the eastern end of Lake Erie, the northern equivalent of the warping is nearly two feet per 

 mile."' For twenty miles north of Oneida Lake, the mean northern uplift is 3.5 feet per mile, 

 and thence, to Cape Rutland 4.5 feet. On' the northern side of Lake Ontario, the eastern 

 equivalent of the uplift is greater than upon the southern side of the lake, increasing 

 from an average of 1.5 feet, west of Scarboro, to nearly three feet per mile at Trenton. 

 Sixty miles farther eastward, this eastern uplift disappears, for there begins to be mani- 

 fested an equivalent of elevation slightly to west of, in place of east of, north, as the 

 axis of simple northward uplift is passed. The passage of the axis of simple northern 



' The Algonquin beach of the Georgian Bay, from whicli this measurement is derived, is not connected with, 

 and is botli older and newer than, the Iroquois Beach. 



- No triangulation can be made on the beach referred to, but its eastern uplift is assumed at the same rate as 

 that of the Iroquois Beach, and deductions therefrom made. 



