36 SEASONAL DEPOSITION IN AQUEO-GLACIAL SEDIMENTS. 
The top of the fine component, therefore, should have the finest material. In 
quiet but shallow water with a depth of say fifteen feet, and with an ice cover- 
ing, such as would prevent wave action, the amount of sediment which would 
settle to the bottom during a winter season might be practically limited to the 
-amount contained in the water at any place when the winter freeze-up came. 
In deep water of 100 or more feet, at an equal distance from the ice, the 
amount of sediment which would settle in a winter season would be greater 
than in the case of shallow water, as such deep water would contain more sedi- 
ment in the beginning of the winter season. Such cases would of necessity be 
limited to fresh-water basins without tidal scour or other disturbing factors. As 
the finest clay particles settle with extreme slowness, when a thin layer of this 
finest clay material is found topping the fine component, it must mean that the 
coarser clay particles have been already deposited and that only this finest clay 
remained to settle. Knowing the very slow rate of settling of clay material, 
it might be inferred that the settling of the material contained in a seasonal 
layer of the glacial clays has taken months rather than weeks or days. If 
the seasonal layers are very thin at one place, but composed of material of the 
same texture as at another locality where the layers are thicker, the water in 
the former case may have been shallower than in the latter, provided, of course, 
that the place of stream emergence was equally distant in both cases. To my 
knowledge this cause for the thickness of layers has not not been suggested 
heretofore. 
F. In certain very favored locations undisturbed records of the weather 
vicissitudes for a year or years might be preserved almost complete. The first 
condition for such a deposit would be a location not very far from the ice front 
where materials were abundant and deposition rapid enough to record minor 
weather fluctuations. At the same time the water should be deep and quiet 
enough to insure deposits already laid down, against erosion and resulting 
destruction of the record. Certain deposits have been made in locations 
approaching these ideal conditions. Records of day and night sedimentation 
might be partially preserved in such locations. 
G. If the land near the ice front should be without ice, snow or vege- 
tation, a high wind in the right direction, blowing over loose sand or silt, would 
have the power to transport sediment for miles into the basin of deposition. 
Some of the thin layers of fine sand found in clays or slates, which are difficult 
to account for, might be due to this cause. Unless the sand grains show evidence 
of wind action, however, such a cause would be difficult to prove (Woodworth, 
4 
