GLACIAL AND 1NTERGLACIAL BEDS 293 



Professor Penhallow, from whose report to the British Asso- 

 ciation in 1900 this list is taken, states that "within this area no 

 less than thirty-eight species have been recovered, and they point 

 conclusively to the existence of climatic conditions differing 

 materially from those which now prevail, and of a character 

 more nearly allied to those of the middle United States of today." 

 " Only one species appears to have disappeared in Pleistocene 

 time. Acer pleistocenicum, which was abundant in the region 

 of the Don, bears no well denned resemblance to existing 

 species." 



The plant remains consist chiefly of wood and leaves, the 

 former usually much flattened from the pressure of the later ice 

 sheet, but otherwise often well preserved, the red cedar, for 

 instance, showing its color and being still quite tough, although 

 some of the wood, probably decayed before being waterlogged 

 and included in the clay, is in a worse condition. Parts of the 

 wood are almost of the nature of brown coal breaking across 

 easily and showing a coaly luster on the broken surfaces. It 

 may be worthy of mention that some large bits of porous 

 charcoal, as if from the burning of a log, were found cemented 

 with limonite in the sand (No. 6) just under the blue clay. 

 The leaves are preserved generally in the thinner beds of clay 

 and are rarely obtained whole. 



The sands of the Don beds vary greatly in fineness and 

 color, and are more or less cross bedded and mixed with gravel, 

 as if deposited under wave action ; while the coarse shingle at 

 the base of the section near the bend of the Don looks like the 

 work of a river. The upper part of the warm climate beds of 

 the Don, consisting of stratified clay (No. 7) and sand (No. 8) 

 appears to have been formed under distinctly lacustrine con- 

 ditions. At the beginning of the formation there may have 

 been no lake, only a great river with a tributary or tributaries 

 coming in from the west ; but at its close there was a great lake 

 which stood at least sixty feet above Lake Ontario at present. 

 Whether the change in water levels was slow or rapid there is 

 no evidence to show. That the water remained for some time 



