96 Wald hOOIRIM AIL ON? (GAZ OIL OG W 
kind. The glacial theory involves the co-operation of pan-ice 
as well as icebergs, or at least recognizes the possibility of this 
co-operation. At the ‘close of (the dmiit period) the melatine 
importance of the results of pan-ice must have depended partly on 
the vertical range of its activity as determined by changes of 
relative level of sea and land, and partly on whether the glacier 
ice subsequently over-rode the zone of the early activity by the 
pan-ice. The known facts concerning the relative changes of 
level of sea and land, and the known facts concerning the nature 
of the drift itself, seem to ascribe by far the larger part of the 
work involved in its production, to glacier ice. The functions 
of other forms of ice seem to have been very subordinate. 
Significance of the abundance of stratified drift. The fact that. 
so much of the drift is stratified has sometimes been thought to 
be a difficulty in the way of the glacial theory. It is certainly 
true that the deposits made by glaciers directly are unstratified ; 
it is certainly true that a very considerable portion of the drift is 
Stratihed. But it is to) be remembered that the ice of jeveny 
extinct glacier, be the same large or small, was converted into 
water upon its dissolution. It is to be remembered that as the 
ice of any glacier moved forward during the period of its growth, 
it was constantly melting, so that, barring the loss by evapora- 
tion, all the ice of any glacier, from its inception throughout the 
whole period of its history to final dissolution, was converted 
into water, and that most of this water ran for longer or shorter 
courses over the surface of land, either beneath or beyond the 
ice, often modifying the surface of the drift already deposited by 
the ice, and often depositing upon it, in bedded form, such grav- 
els, sands, and silt, as fell to its lot to carry and deposit. If north- 
ern North America and Europe were covered by huge ice caps, 
as the glacial theory of the drift supposes, every pound of these 
stupendous ice masses which did not evaporate was sooner or 
later converted into water. According to the glacial theory, there- 
fore, the amount of water which was operative jointly with the ice 
in producing the drift, must have been nearly as great as that of 
the ice itself. It follows that the glacier theory of the drift not 
