The conditions of the deposit of "till" diminished in intensity as the subsidence continued. The gathering ground of local glaciers was lessened, the ice was no longer limited to narrow sounds, but had a wider scope, as well as a freer drift to the southward, and the climate seems to have been improved. The clays deposited had few boulders and many marine shells, and to the west and north there were land-producing plants akin to those of the temperate regions; and in places only slightly elevated above the water, peaty deposits accumulated. The shells of the Leda clay indicate depths of less than 100 fathoms. The numerous Foraminifera, so far as have been observed, belong to this range, and I have never seen in this clay the assemblage of foraminiferal forms now dredged from 200 to 300 fathoms in the Gulf of St. Lawrence. I infer that the subsidence of the Leda clay period and of the interglacial beds of Ontario belongs to the time of the sea beaches from 450 to 600 feet in height, which are so marked and extensive as to indicate a period of repose. In this period there were marine conditions in the lower and middle St. Lawrence and in the Ottawa valley, and swamps and lakes on the upper Ottawa and the western end of Lake Ontario. It is quite probable, nay, certain, that during this interglacial period re-elevation had set in, since the upper Leda clay and the Saxicava sand indicate shallowing water, and during this re-elevation the plant-covered surface would extend to lower levels. This, however, must have been followed by a second subsidence, since the water-worn gravels and loose, far-travelled boulders of the later drift rose to heights never reached by the till or the Leda clay, and attained to the tops of the highest hills of the St. Lawrence valley, 1,200 feet in height, and elsewhere to still greater elevations. This second boulder drift must have been wholly marine, and probably not of long duration. It shows no evidence of colder climate than that now prevalent, nor of extensive glaciers on the mountains; and it was followed by a paroxysmal elevation in successive stages till the land attained even more than its present height, as subsidence is known to have been proceeding in modern times. I am quite aware that the above sequence and the causes assumed are somewhat different from those held by many geologists with reference to regions south of Canada; but must hold that they are the only rational conclusions which can be propounded with reference to the facts observed from the parallel of 45° to the Arctic Ocean.