650 REPORT— 1897. 



then carried forward and widely distributed and commingled with local detritus 

 during alternate recessions and re-advances of the ice-margin, the houlder-clay 

 feeing deposited, to a large extent, by the melting of the ice, as indicated many 

 years ago by J. G. Goodchild in his account of ice-work in Edenside. 



The degrading action of the ice has differed widely in different localities. It 

 is where this action has been most marlied, as around the Fenland border, that the 

 large transported masses of Secondary strata have been most frequently observed. 

 Among examples of such masses are the disturbed sheets of chalk of the Norfolk 

 Coast and Trowse, the huge mass at Roslyn Hole, Ely, and that at Catworth de- 

 scribed by Mr. A. C. G. Cameron. Other well-known examples are the masses of 

 Lincolnshire Limestone at Great Ponton, and the mass of Marlstone 200 yards 

 across at Beacon Hill, described by Professor Judd ; while recently Mr. C. Fox 

 Strangways has observed ' a mass of Lincolnshire Oolite at least 300 yards long 

 and 100 yards broad,' to the north-west of Melton Mowbray. All these occur iu 

 connection with the Chalky Boulder-clay. 



The author then draws attention to the singular absence of Jurassic outliers 

 along the western margin of the great Lincolnshire ' Cliff',' and he suggests that 

 these huge cakes and boulders wee, in some cases, dislodged from outliers which 

 had become frozen to the base of the ice-sheet and were then shifted to higher 

 levels along planes produced in the ice by its movement over an irregular surface. 

 The abundant chalky detritus was no doubt carried along minor planes of move- 

 ment in the ice, the chalk lumps being scored by fractured flint, and the material 

 being transported far and wide at higher levels in the ice than the bulk of the more 

 local material. In certain instances the soil frozen to the base of the ice-sheet was 

 little, if at all, moved, being overridden by subsequent ice-movements. 



The intercalation of sand and gravel with the Chalky Boulder-clay is, he thinks, 

 ?3e8t explained as a marginal phenomenon produced at diflerent stages in the advance 

 find retreat of the ice-sheet. The author acknowledges his indebtedness to Messrs. 

 Chamberlin, Crosby, and Upham, whose studies have thrown so much light on 

 glacial phenomena. 



6. Glacial a)id Interrjlacial Deposits at Toronto. 

 By A. P. Coleman, Ph.D., Toronto University. 



The ravines of the river Don at Toronto and the lake cliffs of Scarborough 

 Heights, a few miles to the east, provide exceedingly interesting sections of the 

 •drift, from 100 to 350 feet in thickness, displaying three or more sheets of till and 

 a varying number of interglacial beds. 



The most important section, at Taylor's brickyard in the Don Valley, shows a 

 lowest till overlying Cambro-Silurian shale of Hudson River age. Upon this rest 

 18 feet of sand and clay, containing many uuios and other shells, as well as leaves 

 and pieces of wood. Some of the unios do not now live in Canadian waters, but 

 are found in the Mississippi ; and several species of trees now belonging to the 

 States to the south occur with them, indicating a climate decidedly warmer than 

 the present. Above this come stratified clay and sand, with a caribou horn and 

 remains of insects and plants belonging to a colder climate than the present. This 

 set of clays and sands is best shown at Scarborough, where the series rises 148 feet 

 above Lake Ontario, and contains many species of extinct beetles, as well as shell- 

 fish, mosses, and wood of hardy trees. 



A complicated middle till overlies these beds, which were deeply eroded before 

 the advance of the ice. Another less important fossil-bearing interglacial bed 

 occurs above the middle till at elevations up to 240 feet above the lake, and is 

 followed by a third till. 



Great changes in the level of the water occurred in connection with these 

 climatic changes, the lake being much lower than at present, before the first 

 glacial advance and after the first interglacial time. 



During the deposition of the middle till, and also while the last sheet of till was 

 being deposited, the water stood from 250 to 300 feet above the jjresent level of 

 the lake, which stands 247 feet above the aea. 



