710 Marvels of the Universe 
air-current, freezes into hail while the drops are falling through the cold substratum of air lying 
between the warm stratum and the earth. Winter hail usually occurs simultaneously over 
large areas, and the hailstones frequently contain tiny air-bubbles. Some possess a few large 
bubbles and air-tubes which radiate from the centre outward. 
Hailstones assume many fantastic shapes. The most usual form is the sphere, though oval 
and pear-shaped stones are found in considerable numbers. These latter are due to the fact that 
the larger round ones, because of their greater weight, fall downwards faster than the smaller 
hailstones and smaller cooled raindrops, and hence overtake and merge into these. Cone-shaped 
hailstones are likewise no uncommon variety. They usually have a more or less spherical base, and 
a particularly fine specimen of this type is shown on page 707. This, with a number of similar stones, 
fell at Morgantown, West 
Virginia, on April 28th, 1877. 
Each measured roughly two 
by one and a half inches, 
with an average volume of 
almost one cubic inch. Per- 
haps some of the most ab- 
normal shapes among hail- 
stones fell at Auxerre in a 
terrific storm, which swept 
over the city on the 29th of 
July, 1871. The stones fell 
in the full blaze of sunlight, 
and owing to the extra- 
ordinary conditions — for 
there was no apparent at- 
mospheric disturbance — 
they preserved their original 
shape. The most character- 
istic forms were sketched by 
M. Naudin, and are shown 
in the four corners of the 
full page. In the centre of 
the same page are two stones 
THE SLUG-LIKE CLION. which were picked up on the 
One of the Shell-less Sea-snails known as “pteropods”’ or “ wing-footed,”’ from the t2th of September 1862 
wing-like expansions on each side of the head. During life it is of a beautiful purple 3 t ao ap 3 
colour and swims in vast shoals at the surface of the Arctic ocean, where it forms the just outside Tiflis. Their 
main source of the food supply of the Greenland Whale. ellipsoidal form is broken up 
into a number of facets much after the manner of a roughly-cut jewel, and a transverse section of 
one of these stones is shown in the upper illustration on ‘page 707. Other peculiar formations are 
shown on page 704. They have been taken from a very early photograph belonging to the 
Meteorological Society. Here the conical form has been broken up into jagged projections, much 
as the spherical stone shown in the bottom right-hand corner of page 709 has been altered by the 
agglomeration of other ice particles. 
In France hailstorms, as a rule, follow the courses of rivers and valleys, and this is especially the 
case when the storm-clouds are low. This fact is borne out by investigation in the countries 
particularly subject to such storms. If, however, there is nothing to cause the storm-cloud to 
deviate from its course, the usual direction is from the south-west to the north-east ; that is to 
say, the direction of their origin—the Atlantic currents. Hailstorms appear to occur in cycles of 
ten years, and those of the greatest violence have occurred in the evenings. 
