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 16½ 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.