when all the grains are separate, and only constrained by the pressure outside the constraining surface.
I have in my hand the first experimental model universe, a soft indiarubber bag with a small aperture to admit of its being filled with small shot; which aperture is partly closed, sufficiently to prevent the shot from coming out, by a glass tube which also serves the purpose of a gauge to measure the dilatation. After filling the bag with small shot, the interstices are filled with highly coloured water, and subjecting the bag to small distortional strains to get the shot in normal piling: then in order to render apparent the inverse behaviour of bag with shot and water under distortional strains we take another similar bag with a similar tube filled only with water and subject both to similar distortional squeezing. When, as was obvious, the water in the tube of the bag without shot rises in the tube; while on the contrary the water in the tube with shot sinks, drawing water from the tube into the bag, as is shown respectively in figs. 9 and 10, and 11 and 12.
It is thus shown that any deformation from the normal piling causes the interstices between the grains to increase, expanding the bag. This
