538 ' TRANSACTIONS OF SECTION C. 



the recession of the Ice-lobes was due to causes acting' locally, and not to mild 

 interglacial periods affecting the whole hemisphere. The phenomena of invasion 

 by successive ice-lobes in the peripheral regions might thus be readily explained 

 without recourse to the Interglacial hypothesis. 



Most of the detailed evidence brought forward in America to support the 

 Interglacial idea is as fragmentary and unconvincing as that of our own country. 

 But there is one notable exception, to which I must particularly refer, as it has 

 been investigated by a Research Committee of the Association, and has, moreover, 

 come under my personal observation. In this case the interglacial deposits, first 

 described by Dr. G. J. Hinde, are magnificently exposed in clifl" sections at Scarboro' 

 Heights, on the shores of Lake Ontario, near Toronto. When I visited these 

 sections under the guidance of my friend Prof. A. P. Coleman, in 1897, they 

 impressed me strongly, inasmuch as they afforded the kind of evidence for which 

 one had sought in vain in Britain. The section around Scarboro' Heights reveals 

 a great mass of fosslliferous stratified deposits, over 180 feet thick, consisting in 

 the lower part of slightly peaty clays, and in the upper part of sands ; and these 

 deposits are overlain by a complex series of boulder-clays, with intercalated beds of 

 sand and gravel, attaining a thickness of at least 200 feet. The fosslliferous clays 

 are the lowest beds seen in the cliff section, but beds belonging to the same series, 

 that are exposed in the Don Valley, on the outskirts of Toronto, are underlain by a 

 few feet of boulder-clay, so that it seems to be beyond question that the Scarboro' 

 beds were deposited in an interval between two epochs of glaciation.^ In their 

 upper part these beds contain a flora and fauna indicating a cool climate, but in 

 their lower portion some of the plants and freshwater shells no longer exist so far 

 north as Cduada, and are therefore considered to denote a climate warmer than 

 that of the present day. On this and other evidence it is clear that during the 

 course of the Glacial Period the whole of the district was for a considerable 

 time released from the ice-sheets which previously and afterwards covered it. 

 Moreover, in the opinion of Prof. Coleman, some of the plants and shells of the 

 warm-climate beds denote conditions that would be incompatible with the persist- 

 ence of ice-sheets anywhere in Canada-: and if this be so, then we here have 

 proof for at least one interglacial epoch. But I still permit myself to feel doubt 

 regarding this last-mentioned deduction, as the shells and plants in question, 

 which have their present habitat in the Middle United States, even yet endure 

 winters of considerable severity ; and there are certain factors in the composition 

 of the beds and their altitude above Lake Ontario that justify caution. It is, 

 however, mainly from my knowledge of this ' Toronto formation,' and of the 

 Kirmingtou section in England, presently to be discussed, that I still maintain an 

 undecided attitude in respect to the Interglacial hypothesis in its simpler form. 



Further support to the probability of an interglacial epoch has been adduced 

 from the history of the great lakes which formerly existed in the Interior Basin of 

 the "Western States. It has been shown by the researches of G. K. Gilbert in the 

 'Lake Bonneville' basin ^ and of I. G. Russell in that of 'Lake Lahontan,'* 

 that there were two separate epochs, during which these enormous basins were 

 filled with water, and an intervening arid epoch, during which they were dried up. 

 The region is one in which the actual glacial phenomena are restricted to the 

 mountain valleys ; but as it seems evident that the lakes were associated in some 

 way with the Glacial Period, the two stages of extension are supposed to repre- 

 sent two distinct epochs of glaciation, separated by a long interglacial drought. 

 The correlation, however, has difficulties, which are very impartially discussed bv 

 Gilbert and Russell ; and it will not admit of more than one interglacial episode' 



' Prof. A. P. Coleman, Reps. British Assoc, for 1898, pp. 522-29; for 1899, pp. 411- 

 414 ; for 1900, pp. ,328-340 ; also (summary and discussion) ' Glacial and Interglacial 

 Beds near Toronto.' Journ. Oeol. vol. ix. (1901), pp. 28.5-310. 



" ' The Duration of the Toronto Interglacial Period.' American Geologist^ vol. 

 xxix. (1902), p. 79. 



3 ' Lake Bonneville.' Monogr. U.S. Geol. Survey, vol, i. (1890), 



* ' Lake Lahontan.' lUd,, vol. xi. (1885), 



