84 TREE PLANTER'S MANUAL. 



HOW HAILSTONES ARE FORMED. 



Judging from the mechanism of hailstones, they rotate around a vertical 

 axis. They are composed of alternate layers of ice and snow laid over each 

 other like the concentric rings of an onion. If the whirling motion be 

 between contiguous rain and snow clouds, it would carry the rain into the 

 snow particles, dusting it and freezing it into hail. There are numerous 

 coatings of ice and snow, indicating a continuous circling of the wind from 

 rain-making into hail, snow and ice-making clouds. If the whirl around a 

 vertical axis dips the water particles in and out of different strata of cloud 

 temperature, warm rain into freezing, snowy air and back into warm air 

 for forming another rain-circle around the icy ball, and so round and round, 

 the products are hailstones, small or large according to the number of times 

 the dipping process has occurred. 



Hailstorms are, therefore, cyclonic, often moving at the -rate of forty to 

 fifty or more miles an hour. They drive on out of the hail-manufacturing 

 belt with terrible fury upon everything they touch. 



PREMONITIONS. 



These disasters occur on the open plains and prairies. They are most 

 frequent in summer, following excessively hot days. They are generally 

 preceded by layers of dark gray clouds, moving in angry whirls, accom- 

 panied by great electric disturbances of heavy lightning and thunder. 



In his elaborate report of 1877, Franklin B. Hough, then acting as chief 

 of the forestry division under the agricultural commissioner, thus credits 

 (page 299) the forest as a 



NEUTRALIZER OP HAILSTORMS : 



"It is attested by M. Becquerel, from numerous observations made in 

 France, that hailstorms become more frequent as woodlands are cleared 

 away, and that although such storms may occasionally pass through a for- 

 est of small extent, they will sometimes change to rain over a woodland, 

 and again to hail beyond; but oftener they will turn aside or divide as they 

 come to a large wooded area. This may be accounted for from the fact 

 that the moist air that hangs over a woodland from the evaporation of the 

 leaves becomes a conductor of electricity, and thus lessens the effect of the 

 storms." 



HAILSTORMS MOVE IN ZONES. 



M. Bailie, in his "Zones des Orages a'Grele," avers that "zones in hail- 

 storms in France are profoundly modified by local causes, appearing with 

 severity in some districts, and leaving others intact. They have a prefer- 

 ence, so to speak, for certain parts of a country, visiting it often, and pro- 

 ducing similar effects, observing therein a singular periodicity, returning 

 &t intervals of a certain number of days and hours for a series of years, so 

 that the periods of two bad years are separated by periods of good years. 

 When they come they seldom come singly." The careful observer may 

 have noticed similar phenomena in our own country, that hailstorms seem 



