HAIL 381 m ? him. He says that at the beginning of the se- verest storm that he ever witnessed, there fell some large drops of rain; these soon ceased, and after a short interval there fell hailstones, shaped like beans, of one or two tenths of an inch in diameter; this ceased, and there fol- lowed rain, and after another pause fresh hail of two or 'three tenths of an inch diameter ; again another pause, and a new fall of hail. Of these successive falls of hailstones, the first possessed only a slight coating of ice over the snowy nucleus ; the second class were par- tially surrounded with a thicker layer of ice ; and the last hailstones were generally rounded masses one third of an inch in diameter. In 1 cases he found the kernel not transparent, hile the surrounding ice was so in a high degree. Another very general peculiarity of hail storms consists in the fact that the central portion of the region passed over by the storm is almost entirely free from the fall of hail- .es, which on the other hand are almost variably found in two or more belts parallel the track of the storm centre, and some dis- ce therefrom./ Thus in the storm of July 3, 1788, which passed from France in a north- erly direction into Holland, the storm ck was about 500 m. in length, and was versed in less than nine hours ; over the itral track, to a breadth of 6 m. on either e, no hail fell, but heavy rain; on either e of this region, to a distance of 5 or 10 m., country was visited with hail of the most uctive kind, by which property valued at re than $5,000,000 was destroyed ; rain also over a district stretching far beyond the Its of hail. Perhaps the most frequent ac- paniment of hail, and the most prominent .uliarity of the hail storm, is found in the charges of electricity, which are usually but t always remarkably severe. While numer- s thunder storms occur without attending il, it is on the other hand generally the case ,t hail storms are also thunder storms. Or- ary thunder storms of a moderate degree severity, as well as tornadoes, waterspouts, d or dust storms, whirlwinds, and hail rms, have many points of similarity, and y be said to pass by insensible shadings one to the other. Peltier enumerates 16 tornadoes or trombes, of which 14 were
- ompanied by hail. Reye, in his work on
'irbelsturme, enumerates 33 tornadoes that rred in America, of which only three are oted as having been accompanied by hail. r ail storms, and indeed all that class of dis- rbances just enumerated, have a local char- ter, and it is believed that in general their 'hs are related to the larger areas of low ba- meter that move over the surface of the rth ; they are more numerous and more in- at those times when the barometric ressure is diminishing in advance of some ex- msive region of low pressure; they may in act be said to be the precursors of, or to ini- ' ,te, some more general atmospheric disturb- ance. Our knowledge of the operations going on in the interior of a hail storm has been ma- terially increased of late years, though still far from being complete ; and the theories of Volta, Olmsted, &c., may be said to possess now only a historical interest. According to Volta, atmospheric electricity plays a very im- portant part in the formation of hail, the snowy nucleus being alternately attracted and repelled by two layers of clouds charged by opposite electricities, and in the mean time continually adding to its size, until its' weight brings it down to the earth. This theory may be regarded as distinct from the earlier elec- trical theories of Musschenbroek, Monge, &c. ; and notwithstanding its many defects, it seems to have been very widely accepted, especially in France and Germany, during the latter part of the 18th century. Montbeillard was led in 1776 by its consideration to propose the use of Franklin's lightning rod as a protection against hail storms; a proposition that has been very widely adopted in France,, but it is believed without producing the desired effect, although a popular and almost superstitious belief prevails in that country in regard to its efficiency. Leopold von Buch maintained that the water was frozen by very rapid evap- oration from the surface of each drop ; a hy- pothesis concerning which Kaemtz remarks that even if it were possible thus to convert rain drops into hailstones, this method of for- mation would not accord with the ordinary saturated condition of the atmosphere in the cloud region. The hypothesis that uprising currents of moist warm air, by their mixture with higher currents of very cold dry air, thereby give rise to the formation of hail- stones, seems to have been first propounded by Muncke, and has, in a more or less modi- fied form, been favored and even adopted by prominent meteorologists in Europe, and has been developed independently by Olmsted in America. More recent writers, as Peslin (1866) and Reye (1864 and 1872), have devel- oped the consequences of the principle first announced in meteorology by Espy, that storms (including in that term every phase of atmospheric disturbance) owe their energy to the condensation of aqueous vapor caused by the cooling consequent on the internal work performed in the ascension of moist air to ele- vated regions of the atmosphere. It is demon- strated by these writers that the rapid ascent of the moist air found near the surface of the ground on a warm summer's day is attended with such a rapid cooling that a portion of the vapor must necessarily be condensed, either as drops of water or flakes of snow and crys- tals of ice. According to Reye, who in this respect is but a disciple of Espy, the phenom- ena of cyclones and hurricanes, of waterspouts and whirlwinds, of thunder storms and hail storms, can all be developed as the conse- quences of a single simple law of the mechani- cal theory of heat, namely, the condensation
