532 SOSERTIMEENGON DLE 
warmth — the warmth the cause of the melting and retreat of the 
ice,and finally that the removal of the ice-load was the cause of 
the re-elevation to the present condition; but—and this is the 
distinctive feature of my view—that in all these cases che effects 
lagged behind the causes. 1 showed that this was so in all cases 
of accumulated effects, but would especially be true in this case. 
To illustrate these relations I used a diagram which I here pro- 
*Serfiary Present 
Fic. 1.—Diagram showing the relations of land elevation and ice accumulation 
during the Quaternary. A&W—course of time and also the present status of earth 
crust. The dotted line shows elevation if it had not been interfered with by the 
ice-load. 
duce. The legend will sufficiently explain it. By this view the 
Quaternary consists of two epochs, the Glacial and the Cham- 
plain, of nearly equal lengths. The one characterized by eleva- 
tion and cold, the other by depression and warmth, but the 
extreme of ice accumulation lagged behind the extreme of 
elevation as seen in the figure. 
I am more and more convinced that the principle of lagging 
is a true one and even more important than I at that time sup- 
posed. I now believe that I did not at that time make the lag- 
ging, especially in the matter of the accumulation of the ice- 
load, great enough. We must make a distinction in this regard 
between the intensity of the cold and the thickness of the 
accumulated ice. The cold probably responded somewhat 
promptly to the land elevation, but not so the ice accumulation. 
This was a very slow process and might lag to any degree 
behind the elevation and the cold. This we now proceed to 
show. 
1. Snowfall depends on cold, but still more upon moisture. 
