Page:The American Cyclopædia (1879) Volume VIII.djvu/394

 380 HAIL jected to a pressure of many atmospheres. Small bits of dust, leaves, and other foreign particles are occasionally found in the interior of the mass of a hailstone, and crystals of sul- phur as well as ashes are particularly observed when the hail storm occurs in a volcanic region. Different Forms of Hail. The small hailstones that fall in storms of sleet are generally regarded as drops of water that have been frozen in their downward passage through layers of cold air ; and their formation is therefore believed to be a different process from that attending the formation of larger hailstones. These latter occur in connection Section of Hailstone, magnified. with a class of storms that are distinctively known as hail storms. The velocity with which large hailstones fall to the ground is often so great that, taken in connection with their mass, they cause very serious devastation ; instances are recorded of animals being destroyed in large numbers, and damage is frequently done to houses, forests, and crops. It is believed that the velocity is indeed usually much less than is due to bodies of their size and density, and several theories have been devised to account for this. Prof. Olmsted supposed that the true reason is found in the retardation occasioned by the nucleus continually taking up in its de- scent accessions of vapor, which immediately before was in a state of rest ; it has however not yet been shown that there is any necessi- ty for such an explanation, since we know too little concerning the altitude above the earth's surface, at which hail is formed. Hail storms occur most frequently in the spring and summer months, and in the warmest part of the day. Kaemtz has shown that in Germany and Switzerland 50 per cent, of these storms occur in the springtime. Wes- selowski shows that in Russia 40 per cent, oc- cur in summer, and 30 per cent, in spring. In the Netherlands and France 40 per cent, oc- cur in spring. It is comparatively rare that hail storms take place between 9 P. M. and 7 A. M. ; 60 per cent, of the storms in Germany occur between noon and 6 P. M. As regards the frequency of hail storms in various por- tions of the globe, it is generally believed that they rarely or never occur in the polar re- gions, and but little more frequently in those portions of the tropical regions whose climate is controlled by the neighboring ocean ; thus they are recorded as of extreme rarity in the islands of Martinique, Mauritius, and in the lowlands of Java and Borneo. On the other hand, in the higher portions of Java, Borneo, and Santo Domingo, hail is by no means infre- quent; in the island of Cuba, according to Poey, over 40 hail storms have been recorded since 1784. In the temperate zone, both in rolling and mountainous countries, hail storms are far more frequent. Of these countries, some, such as France, are peculiarly subject to severe hail storms, while again in every such land many localities are pointed out where it never hails. In general these latter localities are found to be decidedly higher than the aver- age elevation of the surrounding country, or else decidedly lower; thus, according to Sa- vigne, a mountain in the neighborhood of Cler- mont was during 23 years only once visited by hail, while the country about its neighborhood was frequently devastated. In Lithuania hail occurs on the hills more frequently than on the plains, while in Poland it occurs at the foot of the Carpathian mountains more frequently than in the lowlands. Leopold von Buch states that it never hails in regions where cretins are found ; a generalization, however, that does not seem to be accepted by many, and the cause of which must, if the fact be granted, be looked for in some peculiarity common to the regions in question. Among the special phenomena of hail storms may be mentioned the pauses that j occur between successive falls of hail, which I are well described by Kaemtz as observed by