34 SEASONAL DEPOSITION IN AQUEO-GLACIAL SEDIMENTS. 
valley regions, the fine components of the banding are usually represented 
by a large percentage of the finest clay. In certain cases, however, as where 
a glacier has over-ridden sand and gravel deposits for a long distance, the glacial 
streams may not contain much of the finest clay sediment. 
C. To distinguish between the effects due to the composition of the till, 
and to effects due to climatic and other factors, in a study of the ratio between 
the coarse and fine components of the banding, may not be an easy matter. 
The true nature of the climate responsible for our Glacial periods is not well 
enough known to speak with certainty of the weather conditions of those 
times. It appears to be fairly certain, however, that high winds as denoted 
by loess deposits outside some glaciated areas, with much more precipitation 
than we have at present, was characteristic of the several glacial climates 
of the Pleistocene period. What the distribution of temperatures was over 
the year is not well determined. It is even possible that there was more heat 
instead of less heat from the sun, thus producing greater evaporation in the 
equatorial regions and greater precipitation in the northern regions than at 
present, with higher winds. (Tyndall, 1865, p. 205-207; Huntington, 1914, 
p. 477-590). 
Whatever the distribution of temperatures might have been during the 
Glacial epochs, the seasonal layers ought to throw some light on this problem. 
A long cold winter ought to be recorded by a thick layer of the finest sediment, 
and a short summer should be recorded by a thin layer of the silt or fine sand. 
If the time of freeze-up were of short duration the layer of finest sediment 
should be thin, etc. The ratios between the thicknesses of the coarse and fine 
components should be studied rather than the actual thicknesses of the individual 
components, for the thicknesses of the layers are due to other factors in addition 
to the climatic factor. The ratios between coarse and fine components are also 
due to the relative amounts of coarse and fine materials in the till. To distin- 
guish between these causes affecting the ratios it would be necessary to study 
the till from which the clay deposits were derived. 
With interglacial conditions, when the temperature was above the freezing 
point for the greater part of the year, other things being equal, the coarse com- 
ponent should be thicker than the fine. If, during the winter, there were thaws 
of intensity sufficient to inaugurate rapid stream flow, the fine component should 
show evidence of such thaws in coarser, thin layers, intercalated in its midst. 
In case the first great thaw of the spring at the breaking up of the ice, is followed 
by a freeze-up, there should be found near the top of the fine component a layer 
