INTERGLACIAL WATER-LEVELS 173 



water, and extend 15 or 20 feet below the surface, as shown in wells sunk 

 last year by the Pleistocene committee of the British Association for the 

 Advancement of Science, at the foot of the hights. Inland these easily 

 recognized peaty cla3^s rise to 145 feet north of Keservoir park, and have 

 been found near York mills, more than 6 miles north of Toronto bay. 

 How much farther inland they extend is not known. While the peaty 

 clay rises only 95 feet above the lake at Scarboro, a conformable series of 

 stratified sands containing wood and a few fresh water shells rises 50 feet 

 higher, so that the lake in the times of the Scarboro deposits stood at 

 least 145 feet above the present water-level. 



The cause of this deepening of the water from 60 feet or less to 145 feet 

 or more above the present lake is not certain. The climate, as shown by 

 the authorities quoted above, was about that of the north shore of lake 

 Superior or the south shore of Labrador at present. It was not arctic 

 nor even subarctic, but cold temperate. The clays and sands contain no 

 boulders such as one would expect to find in a glacially dammed body 

 of water with large ice masses drifting on its surface, but some beds of 

 clay are crumpled in a way that might suggest the shove of an ice-floe. 

 It seems most probable that the uplift which held back the Don waters 

 increased during Scarboro times, ultimately reaching 145 feet or more at 

 the east end of the basin. The great river which entered the Scarboro 

 water at an unknown distance north of the present shore of Ontario, 

 bringing down fragments of moss, wood, and bark and innumerable 

 drowned beetles from the regions to the northwest, demanded a wide 

 outlet to the sea somewhere toward the east, and probably followed the 

 present valley of the Saint Lawrence. 



Another point suggesting that this body of water in which the Scarboro 

 delta deposits were laid down was not ice-dammed is the fact that before 

 the next great glacial advance the Scarboro water was drained off to a 

 level below that of lake Ontario. The proof of this is to be seen in the 

 section of the Scarboro cliffs, where valleys as deep and wide as those of 

 our present drainage system were carved in the delta deposits before the 

 next till sheet was spread over the region. 



If the reasoning here given be accepted, we must assume that the 

 eastern end of the basin rose 145 or more feet above the western end, as 

 compared with the present lake level, during inter-Glacial times, and 

 then sank again to a point somewhat below the modern water planebefore 

 the ice advanced once more. 



The series of changes just outlined might be accounted for by AVarren 

 Upham's theor}^ that the land is lowered by the pressure of the mass of 

 ice during a glacial advance and rises again when the load is removed. 



XXVI— Bull. Geol. Soc. Am., Vol. 10, 1898 



