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surfaces to which they belong, have not the same vertical 
angle, the surface being exactly such as would be acquired 
by the fragments of a sphere so constituted that the frac- 
ture tended to follow radial lines. 
Owing to the radiation of the surfaces from a common 
vertex and the steps which occur between the vertex and 
the base, the angle of the conical surface of the stone is 
greater near the vertex than near the base. Thus the 
smaller stones appear less elongated than those which are 
larger. 
The fact that in the sketches of actual stones, which 
I gave in my last paper, I showed the steps as less 
pronounced and the angles larger than they are in 
the artificial stones, is probably owing in some measure 
to my having formed my ideas from the observation 
of favourable specimens chosen from amongst those 
which fell. The larger angles were probably also, in 
part, owing to the smaller size of the actual hailstones, which 
were not much more than one fourth of an inch across. 
But I think that it is important to notice that the some- 
what imperfect way in which the outside layers in the 
surface of the artificial stones are continued, may be owing 
to the narrowness of the jet of air which, on striking the 
stone, tends to diverge laterally rather than to flow upwards 
past the sides of the stone, as it would do if the jet were 
broader, or as the air must do when the stone is falling 
through it. 
The rate at which stones can be formed depends on the 
amount of water which can be introduced into the spray, 
the larger stones taking from one to two minutes. At 
first sight this may seem to be somewhat slow, but the 
following estimate tends to show that the artificial are 
probably formed quicker than the actual stones. 
The speed of the jet of air at the point at which the 
stones are formed is nearly equal to that at which the 
larger stones would fall through the air, This is shown by 
