280 THE CANADIAN NATURALIST. [Vol. X. 



but which seems scarcely possible as it is thoroughly unstratified, 

 filled with angular fragments of Niagara limestones and consti- 

 tutinsr a true 



Till. — This forms a possible equivalent for the Boulder clay 

 of the St. Lawrence valley. Principal Dawsou remarks that the 

 Boulder clay, as far as it is a marine deposit, is older on higher 

 levels than on the lower. Now, we find that the western part of 

 the Dundas valley is made up of great hills and valleys often in 

 the form of roches moufonnees, formed largely by the modern 

 denudation of the streams. Sometimes these hills are cut down 

 to a depth of nearly 1 50 feet. Sections of several parallel ranges 

 may be seen by crossing the country from Ancaster to the G. W. 

 Railway, about two miles east of Copetown. The escarpments 

 at these two places are about 500 feet above Lake Ontario, whilst 

 the beds of some of the valleys (as, for example, near the 

 " sulphur springs ") is not more than 240 feet above the same 

 water-level. In this Till, as exposed at the base of the hills, cut 

 away in road-making, I saw only fragments of Niagara limestones, 

 mostly of such thin slabs as the upper layers of the Silurian rocks 

 at Dundas afford ; and these stones make up a large percentage 

 of the whole mass of the bases of the hills. Again, it is possible 

 that these unstratified deposits extend down to the Palaeozoic 

 rocks beneath, which may be absent for a great depth below the 

 level of Lake Ontario, as they are in the centre of the Dundas 

 valley, more than two miles from the nearest portion of the 

 escarpment. It is only after passing the flanks of these hills, far- 

 ther eastward, that we find the Erie clay. Some of these hillocks 

 near their summits have old beaches, others capped with clays. 

 Their summits are mostly composed of clays of the Saugeen 

 equivalent or of alluvium. The source of this Till is the 

 ruins of the Niagara formation, and could hav^e been derived 

 from the upper beds of the rocks of that age, which occur on the 

 summit of the escarpment both at Dundas and Ancaster. 



Dr. Dawson has shown that the Boulder clays of Eastern Can- 

 ada were deposited beneath water and contain remains (though 

 not abundant) of Arctic animals. The marine deposit does not 

 extend westward of the outlet of Lake Ontario, but beyond this 

 meridian the Erie stratified clay, resting on glaciated rocks (gene 

 rally), appears to occupy its place, and is often deposited at levels 

 below the lake surface. However, there is (outside of the Dun- 

 das valley), at least one place where a few feet of Boulder clay 



