No. 5.] SPENCER — SURFxVCE GEOLOGY. 305 



are abundant. They arc abundant in such remnants of the 

 boulder chiy as exist, and in portions of the lower beds of strati- 

 fied clay. At the western end of Lake Ontario they are not 

 found in the Saugeen clay. However, in the later terraces they 

 are found, though usually of small size. On the surface of the 

 country above the Niagara escarpment they are met with much 

 more frequently than below the escarpment (where they are very 

 rare unless derived from one of the beaches). On the upper 

 levels of the Dundas valley none are to be seen. The " Arte- 

 mesia gravel " contains many. It also in places contains large 

 <|[uantities of the water-worn remains of Hudson river rocks, all 

 derived from lower levels. Along Rosseau creek, in Barton 

 township, there is a group of semi-rounded boulders two feet 

 long, composed of Medina sandstones, whose outcrop is only two 

 miles away, but nt an elevation of two hundred feet lower, be- 

 neath the Niagara escarpment. The northern erratics are much 

 more abundant and larijjer on the hiuhlands of New York and 

 Pennsylvania than at lower levels at the western end of Lake 

 Ontario, and occur on top of the terrace deposits. Beside* 

 these deposits and the Devonian pebbles of New York, carried 

 to higher levels, the materials of the beaches are derived more or 

 less from the adjacent rocks. There seems, as far as Ontario is 

 concerned, but one explanation for the lifting of these water-worn 

 pebbles and boulders to higher levels, and that is their trans- 

 portation and elevation by tlie slow agency of coast ice forming 

 in many succeeding years during the time of continental sub- 

 sidence, as we see to-day the large boulders in many of the 

 north-western shallow lakes lifted from their beds, by the action 

 of the thick winter ice, find drifted on some portion of the shore 

 by the prevailing winds, there to be left on the dissolution of the 

 ice, as reef several feet higher than the lake surfaces. Again, as 

 the waters were receding many of the boulders along the coast 

 would again be picked up by the annual ice, and transported 

 to hills, and growing beaches which are now the highlands to the 

 south, while the intermediate deeper beds received but few, 

 rarely dropped by the passing ice. In regions less exposed to 

 currents and shore deposits but little stony material was deposit, 

 ed, as is demonstrated in the upper portion of the Dundas valley 

 and elsewhere. There does not appear to have been a large 

 amount of floating ice, as indicated by the fine material over the 

 beds of some of the old outlets noticed already. 

 Vol. X. T 2 No. 5. 



