DEPOSITS IN OTHER PLACES 251 



sheet blocked the Saint Lawrence. This theory ignores also the fact that 

 later ice-advances — for instance, the Wisconsin — passed right across the 

 interglacial beds, filled the Ontario basin, and spread out a sheet of till 

 and a series of moraines in the States to the south. 



Interglacial Deposits in other Places 



The case for a great inter-Glacial period in the early Pleistocene is, 

 however, much stronger than even the beds at the Don and Scarboro 

 would suggest, for there is evidence to show that similar beds are much 

 more widely distributed. Land and fresh-water shells occur in thick 

 interglacial beds at the west end of Lake Erie,^ and certain beetle-bearing 

 peaty clays at Cleveland, Ohio, are precisely like those of Scarboro, and 

 include two of the extinct species found at Scarboro, while leaves of 

 maple and other trees have been obtained in interglacial beds north of 

 Lake Erie near Port Eowan. Interglacial wood has been found beneath 

 boulder-clay by Doctor Spencer near the bottom of the ancient Saint 

 Davids Valley west of the Whirlpool at Niagara, and Miss Maury has 

 described an interglacial bed near Cayuga Lake, 'New York, containing 

 eleven of the unios, sphaeriums, and other shells of the Don beds. This 

 interglacial stage has left its mark on both sides of the two southern great 

 lakes at points 300 miles apart. 



A series of interglacial deposits 350 to 400 miles to the north of To- 

 ronto presents much the same character. The flattened trunks of trees 

 and the peaty matter are closely like those from the Don. No less than 

 27 outcrops of lignite or peat of this kind are found in the river valleys 

 of the James Bay slope, extending for 150 miles from east to west and 

 for 50 from north to south. The climate in that northern region was 

 mild enough for trees of large size to mature, and Professor Baker, the 

 latest geologist to report on the region, believes that there was time 

 enough for the vegetable matter to be buried and thoroughly carbonized 

 before the next glariation.* Either the ice retreated more than 400 miles 

 beyond Toronto or the ()])ponents of inter-Glacial periods have a second 

 important inter-Glacial interval to account for. That the two sets of de- 

 posits, each demanding a great length of time, were formed contempora- 

 neously seems most probable. 



■'' GeoIoL'icjil Siirvrv ul' (•iiiiiiilii. M)l. xlv. I!>(i1. |i. ]C,f<. A s\iminary report by Doctur 

 Chalmers. 



♦Bureau of Mines. <»nt!iri<,. vol. xx. imrt 1. pp. :i:i4-2."{S. r>etalls of authorllles for 



pi'evlously mentioned localities iii!i.\ he found In "An estimate of post-Olaelal nnfl Inter- 



Olac'lal time in North .Vmcrica." n piiper presented to the (Joolopical Conpress. 



