HAILSTONES AND SNOW.
A hailstone is a curious formation of snow and ice, and most of the
large hailstones are conglomerate in their composition. They are usually
composed of a center of frozen snow, packed tightly and incased in a rim
of ice, and upon this rim are irregular crystalline formations jutting
out in points at irregular distances. Frequently, however, we find them
very symmetrically formed as to outline, and the snow centers are almost
without exception round. Hailstones and hailstorms differ in different
climates, but they are more pronounced in the torrid than in the
temperate zone. Historians give accounts of hailstones of enormous size;
the very large hailstones being undoubtedly aggregations of single
stones that have been thrown together and congealed in the clouds during
their fall to the earth.
It is recorded that on July 4, 1819, hailstones fell at Baconniere
measuring fifteen inches in circumference, and very symmetrically
formed, with beautiful outline. Hailstones in India are said to be very
large--from five to twenty times larger than those in England or
America--seldom less than walnuts and often as large as oranges and
pumpkins. It is recorded that in 1826, during a hailstorm at Candeish,
the stones perforated the roofs of houses like cannon shot, and that a
single mass fell that required several days to melt, weighing over 100
pounds. It is further recorded that on May 8, 1832, a conglomerate mass
of hailstones fell in Hungary a yard in length and nearly two feet in
thickness. Still another instance is recorded of a hailstone having
fallen in 1849 of nearly twenty feet in circumference. This hailstone is
said to have fallen upon the estate of Mr. Moffat of Ord. We will only
ask our readers to listen to one more hailstone story, in which it is
related that during the reign of Tippoo, sultan, a hailstone fell as
large as an elephant. Undoubtedly one of two things was true regarding
this latter story; it was either a very large hailstone or a very small
elephant. The historian fails to give the size of the elephant. There is
no doubt, however, but that hailstones may adhere and form large masses
owing to the violent agitation of the elements that always attends a
hailstorm.
Hailstorms are almost universally attended by constant and heavy thunder
and lightning, together with violent winds. They usually occur on a
very hot day, and when the air is filled to saturation with moisture.
When this is the case a column of air is very highly heated at some
point, when it ascends with great force into the upper regions of the
atmosphere to a greater altitude than is common in the case of ordinary
thunderstorms. Here it meets with an intensely cold body of air, when it
is suddenly condensed and readily frozen as soon as condensed, which not
only forms hailstones, but sets free the energy that has been carried up
in the moisture globules. This results in frequent electrical
discharges, causing great waves of condensed and rarefied air, which, in
the rarefied portions, produces still more intense cold; so that we have
the conditions for a mighty struggle between the elements, which is
intensified by a constant and terrific electric cannonade. Undoubtedly
there are also whirlwinds in the cloud, similar to those that sometimes
visit the earth, which would tend to gather up the hailstones and
aggregate them into large masses. It is a mighty battle between the
moisture-laden, superheated air, ascending from the surface of the
earth, and the powers residing in the upper regions of cold. Nature is
constantly struggling to find an equilibrium of her forces, and a
hailstorm is only one of the little domestic flurries that take place
when she is setting her house to rights. Hailstorms are usually
confined to very narrow limits, and they can prevail on a grand scale
only in hot climates, where we have the conditions for wide differences
of temperature between the upper and lower regions of the atmosphere;
and, also, where the conditions are favorable, for an enormous amount of
absorption of moisture into the atmosphere.
When snow is formed in the atmosphere, the conditions are quite
different from those of a hailstorm; it is usually in a lower plane of
the atmosphere, and there is no violent commotion, as is the case with
the latter. A volume of air laden with moisture comes in contact with a
colder volume of air, when condensation takes place, as in the case of
rain, except that the moisture is immediately frozen. In this case both
volumes of air may be below the freezing point, but one is very much
colder than the other. If the snow reaches the earth it will be because
the air is below the freezing point all the way down. Snow is formed at
all seasons of the year. We may have a snowstorm on a high mountain when
we have extreme heat at sea-level.
In summer time of course the snow melts as soon as it falls into a
stratum of air with a temperature above the freezing point, and
continues its journey from that point as raindrops instead of
snowflakes. In the formation of a snowflake Nature does some of her
most beautiful work. A snowflake first forms with six ice spangles,
radiating from a common center. Shorter ones form on these six spokes,
standing at an angle of about sixty degrees, on each side of each spoke,
of such length and arrangement as to form a symmetrical figure or
flower. They do not always take the same form, but follow the same laws
that govern the formation of ice crystals. The structure of a snowflake
may be often found upon a window pane of a frosty morning. Here,
however, the free arrangement of the parts of a snow crystal are
interfered with by its contact with the window pane, but while floating
gently in the air there is the utmost freedom for the play of nature's
forces as they apply to the work of crystallization.
The difference in structure of snowflakes is chiefly due to the
conditions under which they are formed. If the moisture is frozen too
rapidly the molecular forces that are active in crystallization do not
have time to carry out the work, in its completeness of detail, as it
will where the freezing process, as well as the condensing process, goes
on more slowly.