ON HAIL--THE HAIL-STORMS OF FRANCE--DISASTROUS EFFECTS OF HAIL--THE
HAIL-STORMS OF SOUTH AMERICA--THEIR SURPRISING EFFECTS--ORIGIN AND NATURE
OF HAIL--PERIODICAL FALLS OF HAIL--HAIL CLOUDS--HAILSTONES--THEIR VARIOUS
FORMS--EXTRAORDINARY SIZE OF HAILSTONES.
As hail seems to be nothing more than frozen rain, it is necessary to
collect a few particulars respecting it in this place.
Great Britain is essentially a rain country; but there are some parts of
the world which have obtained the unhappy distinction of being _hail_
countries: such, for example, as some of the most beautiful provinces of
France, which are frequently devastated by hail-storms. One of the most
tremendous hail-storms on record is that which occurred in that country
in July 1788. This fearful storm was ushered in by a dreadful and almost
total darkness which suddenly overspread the whole country. In a single
hour the whole face of nature was so entirely changed, that no person who
had slept during the tempest could have believed himself in the same part
of the world when he awoke. Instead of the smiling bloom of summer, and
the rich prospects of a forward autumn, which were just before spread
over the face of that fertile and beautiful country, it now presented the
dreary aspect of an arctic winter. The soil was changed into a morass;
the standing corn beaten into a quagmire; the vines were broken to
pieces, and their branches bruised in the same manner; the fruit-trees of
every kind were demolished, and the hail lay unmelted in heaps like rocks
of solid ice. Even the robust forest trees were incapable of
withstanding the fury of the tempest; and a large wood of chesnut trees,
in particular, was so much damaged, that it presented, after the storm,
little more than bare and naked trunks. The vines were so miserably
hacked and battered, that four years were estimated as the shortest
period in which they could become again in any degree productive. Of the
sixty-six parishes included in the district of Pontoise, forty-three were
entirely desolated; while, of the remaining twenty-three, some lost
two-thirds, and others above half their harvest.
This storm began in the south, and proceeded in two parallel bands from
the south-west to the north-east; the extent of one of them being 175
leagues, and of the other 200; thus traversing nearly the whole length of
that great kingdom, and even a portion of the Low countries. The mean
breadth of the eastern portion was four leagues, and of the western two:
and, what is very remarkable, the interval between the two bands,
amounting to five leagues, was deluged with heavy rain. The largest of
the hail-stones weighed half a pound each.
The progress of this storm, which was from south to north, was at the
rate of 16.5 leagues an hour; and the velocity of the two bands was
precisely the same. The continuance of the hail was limited to seven or
eight minutes, at each of the principal stations marked.
There are instances, however, on record, in which hail has produced even
more tremendous results than those above recorded. In some parts of
South America hail-stones are sometimes so large and so hard, and fall
with such violence, that large animals are killed by them. Mr. Darwin,
encamping at the foot of the Sierra Tapalguen, says:--"One of the men had
already found thirteen deer lying dead, and I saw their fresh hides.
Another of the party, a few minutes after my arrival, brought in seven
more. Now I well know that one man without dogs could hardly have killed
seven deer in a week. The men believed they had seen about fifteen dead
ostriches, (part of one of which we had for dinner;) and they said that
several were running about evidently blind in one eye. Numbers of small
birds, as ducks, hawks, and partridges, were killed. I saw one of the
latter with a black mark on its back, as if it had been struck with a
paving-stone. A fence of thistle-stalks round the hovel was nearly
broken down; and my informer, putting his head out to see what was the
matter, received a severe cut, and now wears a bandage. The storm was
said to have been of limited extent: we certainly saw, from our last
night's bivouac, a dense cloud and lightning in this direction. It is
marvellous how such strong animals as deer could thus have been killed;
but, I have no doubt, from the evidence I have given, that the story is
not in the least exaggerated." Dr. Malcolmson informed Mr. Darwin, that
he witnessed, in 1831, in India, a hail-storm, which killed numbers of
large birds, and much injured the cattle. These hail-stones were flat;
one was ten inches in circumference; and another weighed two ounces.
They ploughed up a gravel-walk like musket-balls, and passed through
glass windows, making round holes, but not cracking them.
There is much in the origin and formation of hail that cannot well be
explained. Volta regarded the formation of small flakes of ice, the
kernels of future hail-stones, in the month of July, during the hottest
hours of the day, as one of the most difficult phenomena in nature to
explain. It is difficult to account for the comparative scarcity of
hail-showers in winter; as also, for the great size which hailstones are
often known to attain.
It appears from certain resemblances in the descents of rain, snow, and
hail, that they have a common origin, their different formations being
explained by difference of temperature. Howard has observed a huge
nimbus affording hard snowballs and distinct flakes of snow at the same
time. Hail and rain are by no means uncommon from the same cloud. The
size of a cloud may be such, or clouds may exist in different elevations,
which in an upper region produce hail, in a lower region snow, and at a
still lower elevation rain. Rain may also form in an upper region of the
sky, and descend into a colder stratum of the atmosphere, and be frozen
into hail. Hail generally precedes storms of rain.
Change of wind and the action of opposite currents, so necessary for the
production of rain, are also frequent during hail-storms. While clouds
are agitated with the most rapid motions, rain generally falls in
greatest abundance; and if the agitation be very great it generally
hails. Before the descent of hail a noise is heard, a particular kind of
crackling, which has been compared to the emptying of a bag of walnuts.
The descent of hail in some countries appears to occur at particular
periods. In the central parts of France, Italy, and Spain, it usually
hails most abundantly during the warmest hours of the day in spring and
summer, and in Europe generally it falls principally during the day; but
there are examples recorded of great hail-storms which have taken place
during the night. Near the equator, it seldom hails in places situated
at a lower level than 350 fathoms, for, although the hail may be formed,
the warmth of the regions prevents it from falling in that state.
The appearance of hail clouds seems to be distinguished from other stormy
clouds by a very remarkable shadowing. Their edges present a multitude
of indentations, and their surfaces disclose here and there immense
irregular projections. Arago has seen hail-clouds cover with a thick
veil the whole extent of a valley, at a time when the neighbouring hills
enjoyed a fine sky and an agreeable temperature.
Hailstones of similar forms are produced at similar levels. They are
smaller on the tops of mountains than in the neighbouring plains. If the
temperature or the wind alter, the figures of the hailstones become
immediately changed. Hailstones of the form of a six-sided pyramid have
been known to change, on the wind changing to the north-east, to convex
lenses, so transparent and nicely formed, that they magnified objects
without distorting them. Some hailstones are globular, others elongated,
and others armed with different points.
In the centres of hailstones small flakes of spungy snow are frequently
found, and this usually is the only opaque point in them. Sometimes the
surface is covered with dust, like fine flour, and is something between
hail and snow. This never falls during summer in southerly countries.
In the Andes hailstones from five to seven lines in diameter are
sometimes formed of layers of different degrees of transparency, so as to
permit rings of ice to be separated from them with a very slight blow.
In Orkney, hailstones have fallen as finely polished as marbles, of a
greyish white colour, not unlike fragments of light-coloured marble.
Hailstones are often so hard and elastic, that those which fall on the
stones rebound without breaking to the height of several yards; and they
have been known to be projected from a cloud almost horizontally, and
with such velocity as to pierce glass windows with a clear round hole.
On the 7th May, 1822, some remarkable hailstones fell at Bonn, on the
Rhine. Their general size was about an inch and a half in diameter, and
their weight 300 grains. When picked up whole, which was not always the
case, their general outline was elliptical, with a white, or nearly
opaque spot in the centre, about which were arranged concentric layers,
increasing in transparency to the outside. Some of them exhibited a
beautiful star-like and fibrous arrangement, the result of rows of air
bubbles dispersed in different radii. The figures at the head of this
chapter show the external and internal appearances of these hailstones.
The smaller figures represent pyramidal hail, common in France, and
occasionally in Great Britain.
Brown hailstones have been noticed. Humboldt saw hail fall of the colour
of blood.
On the 15th July, 1808, Howard noticed, in Gloucestershire, hailstones
from three to nine inches in circumference; appearing like fragments of a
vast plate of ice which had been broken in its descent to the earth.
On the 4th June, 1814, Dr. Crookshank noticed, in North America,
hailstones of from thirteen to fifteen inches in circumference. They
seemed to consist of numerous smaller stones fused together.
On the 24th July, 1818, during a storm in Orkney, Mr. Neill picked up
hailstones weighing from four ounces to nearly half a pound.
[Picture: Rain gauges]