﻿492 M. A. Heim on Glaciers. 



out the mass : we have here an infinite number of mutually equi- 

 valent points of action for the force. 



If the above explanation of the origin of glacier-ice is correct, 

 it must be possible to produce also in compact water-ice, artifi- 

 cially, a breaking up into fragments analogous to the glacier- 

 grains ; and in this I have actually succeeded. Had Professor 

 Tyndall, in his experiments on the moulding of ice, not put in 

 operation so strong a pressure that the ice must have instanta- 

 neously burst into fine powder, had he not suddenly compelled 

 it to so great a change of form, and had he experimented on 

 larger masses, a granular structure would have been visible in 

 the moulded ice. His glacier-grains were as fine as powder, 

 and hence escaped observation. 



In a block of wood a tray-shaped depression was cut about 1 

 foot broad, and 6 inches long ; the radius of its curvature was 

 2 feet 6 inches ; and a piece of wood was cut so as to fit into 

 the cavity. Between these two parts of the mould a flat plate 

 of river- ice, beautifully clear, about 2 inches thick, was placed, 

 exactly as long and broad as the cavity ; and the whole was firmly 

 enclosed with boards to prevent the escape of the ice. A stroke 

 with a weight-stone of half a hundredweight, brought down 

 upon it, was sufficient to crush the flat plate of ice into the shape 

 of the cavity. 



A main imperfection in this experiment is that here a nearly 

 equal pressure does not, as in the glacier, operate simultaneously 

 on every part of the mass to be moulded, but the pressure acts 

 on different parts of the plate of ice in succession, not simulta- 

 neously, although within the brief time of the stroke; conse- 

 quently the effect cannot be equal throughout the entire mass 

 as in the glacier. The experiment would be improved if the 

 shape of the cavity could be slowly altered — perhaps by the 

 plate of ice, squeezed between two flexible steel plates instead of 

 in a wooden mould, being slowly curved. On account of the 

 imperfection indicated, the fragments exhibit conchoidal fracture 

 (concentric streaks). 



Between the two parts of the mould, and bent to its concavity, 

 there now lay a mass of ice divided by cracks into grains. These 

 varied in volume from not quite a cubic centimetre to about six 

 times as much ; and between them there lay frequently fine 

 splinters of ice. In one case the ice mass thus moulded, lying 

 in the hollow, was kept cold, and from time to time sprinkled 

 with water ; in a second case it was placed where in the daytime 

 the sun produced a slight melting, but during the night the 

 temperature sunk considerably below 0° C. ; and in the third, it 

 was placed, under a continuous pressure of half a hundredweight, 

 for two days in a room, the temperature of which, except during 



