energy of the blow.

(2) In the case of faces with sharp edges, the process described allows
this heat to be clearly indicated.

(3) The development of heat is greatest where the shearing of the
material is strongest. This shearing is therefore the mechanical cause
which produces the heating effect.

(4) With a blow of sufficient energy and a bar of sufficient size, about
80 per cent. of the energy reappears in the heat.

(5) The figures formed by the melted wax give a sort of diagram, showing
the distribution of the heat and the character of the deformation in the
bar.

(6) Where the energy is small the calculation of the percentage is not
reliable.

So far we have spoken only of cases where the anvil and monkey have
sharp faces. Where the faces are rounded the phenomena are somewhat
different. Figs. 7 to 12 give the area of melted wax in the case of bars
struck with blows gradually increasing in energy. It will be seen that,
instead of commencing at the edges of the indent, the fusion begins near
the middle, and appears in small triangular figures, which gradually
increase in width and depth until at last they meet at the apex, as in
Fig. 12. The explanation is that with the rounded edges the compression
at first takes place only in the outer layers of the bar, the inner
remaining comparatively unaffected. Hence the development of heat is
concentrated on these outer layers, so long as the blows are moderate in