218 BULLETIN OF THE 
relations to the bed rock, divided into three zones. Next the margin 
there would be a belt occupied by completely frozen water, which lay 
upon the bottom ; within this belt, a section where the pressures were 
sufficient to produce only a partial melting or softening of the ice; 
and in the central part of ,the field, an area in which the ice rested on 
pressure molten water, or on ice which was made by the combined 
action of pressure and heat so soft that it could not exercise any erosive 
effect. Iam not inclined to believe that this body of water, reduced 
from the state of ice to the fluid or semi-fluid condition, would ever be 
likely to become of any great depth. As soon as the measure of liquefac- 
tion was brought about which would prevent the ice from holding firmly 
to the bed rock, the heat due to the shearing motion of the glacier and 
to the grinding up of mineral matter would no longer be produced. At 
that stage I conceive that the motion in the inner parts of the field 
which conveyed the annual rainfall towards the margin would in part 
be affected by the gradual working out of the pressure molten water, 
and in part by the squeezing of the softened ice near the base towards 
the glacial front. Neither of these actions would serve to convert any 
considerable part of the energy of position of the mass into heat. 
It is commonly supposed that the immediate application of pressure 
will serve to melt a mass of ice, even if its temperature be a degree or 
two below the freezing point. Some experiments made under my direc- 
tion by Mr. R. W. Wood while a student in Harvard College have shown 
that this is not the case.* If to such a mass of ice even a great pressure 
is suddenly applied, only a small amount of water becomes melted : this 
pressure molten fluid abstracts heat from’ the remainder of the ice in 
such a measure that, if the pressure be rapidly accumulated so that 
the ice has no chance to gain in temperature from without, we have a 
result which apparently contradicts the hypothesis which is here pre- 
sented. I see no reason to doubt that, if we could at once impose upon 
a surface a glacier having the thickness of a mile and a temperature of 
31° Fahrenheit, we should have but little indication of pressure melting 
at the base of the ice; but here, as elsewhere, the element of time and 
the continuity of slight actions have to be taken into account. Reck- 
oning with these, we perceive that the friction of such a hypothetical 
glacier on the bottom, the grinding of the débris which it will produce, 
and the vast amount of shearing action which would take place in the 
particles of ice as they struggled over the surface, and by each other 
for a great distance above the bottom, together with the heat poured 
* See American Journal of Science, 1891, Vol XUT. p. 30. 
