24 
Under these circumstances therefore the particles will not 
traverse the spaces which separate them, and there can be 
no aggregation so as to form raindrops or hailstones. 
If, however, from circumstances to be presently consi- 
dered, some of the particles of the cloud or fog attain a larger 
size than others, these will descend faster than the others, 
and will consequently overtake those immediately beneath 
them, with these they may combine so as to form still larger 
particles, which will mo^/e with greater velocity and more 
quickly overtaking the particles in front of them wiU add to 
their size at an increasing rate. 
Under such circumstances therefore the cloud would be 
converted into rain or hail according as the particles were 
water or ice. 
The size of the drops from such a cloud would depend 
simply on the quantity of water suspended in the space 
swept through by the drop in its descent, that is to say, on 
the density and thickness of the cloud below the point from 
which the drops started. 
My object in this paper is to suggest that this is the actual 
way in which raindrops and hailstones are formed. 
I was first led to this conclusion from observing closely 
the structure of ordinary hailstones. 
Although to the casual observer hailstones may appear 
to have no particular shape except that of more or less im- 
perfect spheres ; on closer inspection they are seen all to 
partake more or less of a conical form with a rounded base 
like a sector of a sphere. 
In texture they have the appearance of an aggregation of 
minute particles of ice fitting closely together, but without 
any crystalization such as that seen in the snow-flake; 
although the surface of the cone is striated the striae radi- 
ating from the vertex. 
Such a form and texture as this is exactly what would 
result if the stones were formed in the manner described 
above. When a particle which ultimately formed the vertex 
