152 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. I. 



ing on this matter, viz., that between the capacity of a soil to hold water 

 or its absorptive power, and its perviousness. 



For instance. Prof. Schubler, of Tlibingen, states as the result of 

 experiment that — 



Sand holds by attraction per lOO parts, 25 parts by weight of water. 

 Loamy soil " 40 " 



Clay loam " 30 " 



Pure clay " 75 " 



Thus we see that perviousness is the opposite of capacity to hold 

 moisture, as the most impervious soils have the greatest power to hold 

 moisture within their interstices. The fact in drainage is a familiar one 

 that where a clay has been puddled — for instance, where the heavily 

 loaded waggon passes over a road — the clay particles become so closely 

 pressed together that it becomes impervious until the moisture and the 

 frost have disintegrated it again. Deep clay soils may similarly become 

 through pressure in large degree impervious. 



Now, we have already seen how, in different portions of the Province 

 the superficial drift deposits 13'ing upon the rock vary notably in char- 

 acter, and how the layers which succeed each other may alter in some 

 instances within a few feet. These variations have depended, of course, 

 upon the condition which existed at the time of their deposition. 

 Remembering that from the melting glaciers and icebergs of the post- 

 glacial era the detritus would follow the order which we can observe 

 after a storm in any stream, we would expect to find what we do find, 

 viz.: that the heavier boulders, gravels and sands would settle first along 

 shores and in the shallow waters, and that the argillaceous materials, 

 remaining longer in suspension, would last deposit in the outer and deeper 

 waters. Currents, variations in the outlines of the shore, and all the 

 other phenomena seen daily in lake or stream, must be looked to for an 

 explanation of the local variations, to which we must add the denudation 

 and innumerable rearrangements due to the floods of primeval mighty 

 rivers, and the varying levels which have given us our system of lakes of 

 varying levels. 



This importance of the order of post-glacial materials has an interest- 

 ing and very practical bearing upon the volume and direction of ground 

 waters. To refer once more to the illustration given, we find the general 

 character of the soils over Waterloo and Perth to be calcareous sands and 

 gravels. Where these lie upon the rock we can see that there will be 

 water-bearing strata of pervious layers, which may be continuous 

 for many miles, and thus supply a vis a tergo pressure of enormous 



