290 M. De la Rive oii the Formation of Hail. ^ 



escape from it, which inundated spaces which were very circum- 

 scribed. As soon as a large quantity of water had escaped from 

 the cloud, it became lighter, was again carried along by the 

 wind, and disappeared at the horizon. This phenomenon was 

 repeated many times during the course of an hour : but by this 

 time the west wind had collected a great number of clouds, 

 which formed an immense curtain, extending over the whole 

 vault of the heavens. The south wind pushed under this stra- 

 tum of vapour additional white clouds, which came with great 

 velocity. The wind became violent and very cold on the sum- 

 mit of the Puy-du-Dome. The lower stratum of the clouds 

 was not like the upper, uniform, but was composed of numerous 

 coloured flocculi, which advanced in the same direction, but at 

 unequal distances, and with different velocities. The brightest 

 flashes of lightning illuminated them from time to time, and the 

 thunderbolts, like furrows of light, passed from one cloud to an- 

 other, sometimes an extended flash seemed even to traverse, at the 

 same moment, the space which separates the Puy-du-Dome from 

 the Mont-Dore. All these phenomena occurred in the lower 

 strata of vapours, and I never saw the electric spark traverse the 

 stratum of air which separated the two layers of clouds. I per- 

 ceived the hail in the distance precipitate itself from the lower 

 clouds and fall to the earth ; I saw it distinctly at the distance 

 of fifty yards from the summit of the Puy-du-Dome, and before 

 my face. The cloud whence it escaped had indented edges, and 

 exhibited in these edges a whirlwind kind of movement which it 

 is diflicult to describe : it seemed as if each hailstone was forced 

 forward by an electric repulsion. Some escaped from beneath, 

 others sprang out from above, so that they flew off' in all direc- 

 tions, and would assuredly have reached the earth in many dif- 

 ferent courses, if the south wind, which was beneath the west 

 wind, had not blown them all towards the north. After five or 

 six minutes of this extraordinary agitation, in which the anterior 

 edges only of the cloud seemed to participate, the hail ceased, 

 order was re-established, the hail cloud, which had continued to 

 advance very rapidly, continued its route towards the north, 

 allowing us to perceive in the distance some sprinklings of rain, 

 which scarcely reached the earth's surface, appearing rather to 

 be dissolved in the lower strata of the atmosphere. 



