27 
The hailstones are clearly aggregations of small frozen 
particles such as those which form a cloud. Nor is it 
possible that they can have been drawn together by some 
electrical attraction; for whatever such attraction, we can 
conceive it will not explain the conical shape of the stones 
or their increase in density towards their thicker sides, 
These clearly show that the particles have aggregated from 
one direction, and with an increasing force as the size of the 
stone has increased. 
It appears as though it might be possible to make arti- 
ficial hailstones. If a stream of frozen fog were driven 
against any small object, then the frozen particles should 
accumulate on the object in a mass resembling a hailstone. 
Not seeing my way to obtain such a stream of frozen fog, 
I thought it might be worth while to try the effect of 
blowing very finely-powdered plaster of Paris. I therefore 
introduced a stream of this material into a jet of steam, 
issuing freely into the air ; (which I hoped would moisten 
the powdered plaster sufilciently to cause it to set firmly 
into whatever form it collected.) The jet was directed 
against a splinter of wood. 
In this way I obtained masses of plaster very closely 
resembling hailstones. They were all more or less conical, 
with their bases facing the jet. But as might be expected, 
the angles of the cones were all smaller than those of the 
hailstones. Two of these figures are shown in the sketches 
annexed : 
f 
PERFECT HAILSTONE. BROKEN HAILSTONE. 
