ram buried in x; and T the string to which it is tied. Now, on
considering fig. 2, where a series of balls are drawn on a larger scale
and on a plane surface, it is clear that the ball A cannot move in any
degree to the right or the left without disturbing the entire layer of
balls on the same plane as itself: its only possible movement is
vertically upwards. In this case, it disturbs B1 and B2. These, for the
same reason as A, can only move vertically upwards, and, in doing so,
they must disturb the three balls above them, and so on. Consequently,
the uplifting of a single ball in fig. 2, necessitates the uplifting of
the triangle of balls of which it forms the apex; and it obviously
follows from the same principle, that the uplifting of S, in the depth of
X, in fig. 1, necessitates the uplifting of a cone of balls whose apex is
at S. But the weight of a cone is as the cube of its height and,
therefore, the resistance to the uplifting of the dateram, is as the cube
of the depth at which it has been buried. In practice, the grains of sand
are capable of a small but variable amount of lateral displacement, which
gives relief to the movement of sand caused by the dateram, for we may
observe the surface of the ground to work very irregularly, although
extensively, when the dateram begins to stir. On the other hand, the
friction of the grains of sand tends to increase the difficulty of
movement. The arrangement shown in the diagram, of a spring
weighing-machine tied to the end of a lever, is that which I have used in
testing the strain the dateram will resist, under different
circumstances. The size of the dateram is not of much importance, it
would be of still less importance in the theoretical case. Anything that
is more than 4 inches long seems to answer. The plan succeeds in a dry
soil of any description, whether it be shingly beach or sand.

Bushing a Tent means the burying of bushes in the soil so far as to leave
only their cut ends above the ground, to which a corresponding number of
tent-ropes are tied.

Tent-poles.--When a tent is pitched for an encampment of some duration,
it is well to lay aside the jointed tent-pole, and to cut a stout young
tree to replace it: this will be found far more trustworthy in stormy
weather. If the shape of the tent admits of the change, it is still
better to do away with the centre pole altogether; and, in the place of
it, to erect a substantial framework of poles, which are to be pl