THE HAMILTON ASSOCIATION. 29 



Meanwhile, what was going on at the lower level, Lake Ontario ? 

 The deposits were being laid down in a series of terraces, and from 

 the fact that the Medina red rock weathered forms the surface soil 

 in many places, we may infer that powerful currents were carrying 

 eastward much of the clay and sand of that day. The formation of 

 the terraces could easily go on contemporaneously with the deposi- 

 tion of clay and sand in the upper area, and, as the water was drain- 

 ed away, the terraces remained high and dry. Indeed, so far as the 

 writer's observations have gone, all but the second terrace were ex- 

 posed somewhat suddenly, since there is no boulder pavement a 

 little below their level, as there would be if the water had broken 

 against their faces for a considerable time. Again, as has been said 

 before, in some cases we rise imperceptibly from terrace to terrace 

 over a succession of billowy meadows and fields, which are 

 often intersected by little streams ; precisely what we should expect 

 to find in a suddenly drained area. The cause of this sudden 

 drainage has been shewn by Dr. Spencer to be the removal of a bar- 

 rier of some kind at the Thousand Islands, thus allowing a vast in- 

 crease in the volume of water pouring seaward down the Saint Law- 

 rence. Meantime the creeks of the district had commenced to cut 

 their way down the escarpment and to form valleys of their own. 

 Probably the second terrace, the most conspicuous feature, occupied 

 more time than the others in its formation, especially since it has 

 been traced so far and so successfully, and since it is fronted by such 

 a well marked boulder pavement. Finally, the latest deposits were 

 laid down, and the present levels of land and water defined. 



To sum up, the writer's observations seem to point to the fol- 

 lowing phenomena : — 



1. A northward extension of Lake Erie, as has been said, the 

 topography of which consisted of a large southward extending sandy 

 island, occupying Oxford, Norfolk, Brant and West Wentworth 

 Counties, as also parts of Middlesex and Elgin. East and west of 

 this were areas of sheltered water, that on the east embracing Lincoln, 

 Haldimand, East Wentworth, northern part, and Welland, having the 

 Niagara escarpment as its northern margin. 



2. From some reason or other, a breaking of the barrier at 

 Queenston Heights, a development of Niagara River, and a vast dim- 

 inution in the volume of water in Lake Erie ; simultaneously, a break- 



