the Theory of Hail. Ill 



pullet's egg, but some as large as a turkey's. There were 

 two strata of clouds, one over the other, and two winds from 

 different quarters, both which conditions he considers necessary 

 for the production of hail. Early on the morning of July 

 28th, 1835, the sky was cloudless, but about 10 a.m. the heat 

 became intense, and at noon almost intolerable. Thin flakes 

 of vapour were seen floating at a great distance, the wind 

 was 1ST. but feeble. At 1 p.m. it had freshened, and white 

 clouds had descended considerably, and soon after covered a 

 great part of the horizon. They were of a greyish tint, 

 which became darker and darker till nearly black, and at 

 2 p.m. they covered the whole of Auvergne. Flashes of 

 lightning were seen, and a distant low murmuring sound was 

 heard, when a vast cloud advanced from W. to E., pure white 

 in some places, chiefly at the edges, and deep grey at the 

 centre: it seemed to advance rapidly under the impulse of a 

 violent west wind, and it sailed below all the other clouds ; 

 its borders were festooned and deeply slashed, and pro- 

 tuberances in the shape of long nipples were suspended from 

 the lower portion. At 2.15 the cloud had approached nearer 

 and the noise became very intense, the edges of the cloud 

 seemed to be in rapid motion, and hail was apparently within 

 it. Soon after this whirlwind kind of motion hail fell, and 

 did much damage, it being propelled by the N. and the W. 

 wind, it took the mean direction. The hailstones that now 

 fell succeeded one another very slowly, but all at once there 

 was an immense downpour. After this the distant rolling 

 sound entirely ceased, and the cloud, freed from its swelling 

 appendages, was carried away by the wind, and the storm 

 was over. 



It was from narratives such as the above that meteorologists 

 began to turn their attention from electricity to the cyclonic 

 action of the wind, as the efficient cause of the formation of 

 hail. Thus Kamtz attributed such formation to the low 

 temperature of the upper atmospheric strata in which the 

 watery particles solidify, and Muncke to the meeting of cold 

 and warm winds. Sir John Herschel 24 also suggested that 

 the generation of hail seems always to depend on some very 

 sudden introduction of an extremely cold current of air into 

 the bosom of a quiescent, nearly saturated mass. So long 

 ago as 1830 Professor Olmsted 2 ^ realized this idea by means 

 of the cyclone, in which a mass of air revolving round an axis 

 more or less inclined to the earth is more or less highly 

 rarefied at or about its vortex, and is thus in a condition to 



24 Scientific Essays. 



25 Anieiican Journal of Science, x-vii. p. 1. 



