218 BULLETIN OF THE 



relations to the bed rock, divided into three zones. Next the maririn 

 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 pi'oduce only a partial melting or softening of the ice ; 

 and in the central part of the held, an area in which the ice rested ou 

 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. I am not inclined to believe that this body of water, reduced 

 from the state of ice to the fluid or serai-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 pai't 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. E. 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 : tliis 

 pressure molten fluid abstracts heat fi'ora 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 debris 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, 1801, Vol XLI. p. 30. 



