16 
the paper was to explain the manner in which the minute 
cloud particles aggregated so as to form raindrops and hail- 
stones. 
Aggregation resulting from the more rapid descent of 
the larger particles. 
I commenced by pointing out that as the suspended 
particles of water or ice which constitute a cloud are all 
descending with velocities which increase with their size, 
the larger particles will descend faster than the others, and 
will consequently overtake those immediately beneath them; 
with these they will combine so as to form still larger 
particles which will move with greater velocity and more 
quickly overtaking the particles in front of them, will add to 
their size at an increasing rate — and I then proceeded to 
consider how far this was a sufficient, as well as a necessary, 
cause of the phenomena of hail and rain. One of the most 
important points on which my arguments were based was 
The Shape and Structure of ordinary Hailstones. 
On close observation I had found what had previously been 
noticed by other observers, that the shape of an ordinary 
hailstone is not what at first sight it appears to be. They 
are not spheres more or less imperfect, but more or less 
imperfect cones or pyramids with rounded bases like the 
sections of spheres ; the conical surface being striated, the 
striae radiating from the vertex of the cone. 
In texture the hailstones have the appearance of being 
an aggregation of minute particles of ice fitting closely 
together but without any crystallization, such as that seen 
in the snow-flake, while, on careful observation, it is seen 
that they are denser and firmer towards their bases or 
spherical sides than near the vertex of the cone, which 
latter often appears to have been broken off in their descent. 
As I explained, it seemed to me that this form and struc- 
ture was exactly such as would result from the manner of 
