the Theory of Hail. 175 



storms, dating from the year 1449 to his own time. One 

 example will suffice for oar present purpose. At midnight, 

 between the 25th and 26th June, 1822, a violent storm of hail 

 burst over Meissen, and the next morning the farmers had to 

 mourn the entire loss of their crops of fruit and grain, and 

 thej found hundreds of starlings lying dead in the fields. 



Another objection with respect to the sun is that, if it 

 promotes evaporation, it also raises the temperature, as was 

 shown by Bellani 20 , who covered the bulbs of two thermo- 

 meters with wet linen, and exposed one to the sun and the 

 other to the shade. Evaporation was the more rapid in the 

 sunshine, but the temperature was higher; whereas, according 

 to the theory, it ought to have been lower, even to freezing. 



The celebrity of Volta's name gained for his theory much 

 attention, and with some modifications it was more or less 

 adopted. Perhaps the most distinguished physicist who 

 quarrelled with it, and yet put forth a theory very much like 

 it, was Peltier 21 , who, in announcing it, complacently remarks 

 that " Volta a place des suppositions ou je place des faits." 



Peltier also imagines two clouds in opposite electrical states, 

 placed one above the other. Their mutual attraction is con- 

 siderable ; they approach without any notable discharge, but 

 the electricities are exchanged, and there can be no such 

 exchange without producing vaporization of the minute drops 

 or vesicles which compose the clouds. Hence there is a 

 lowering of temperature, rapid in proportion to the electric 

 tension of the two clouds. Should the temperature of the 

 clouds be considerable, no noticeable effect ensues ; but if one 

 be at or below the freezing-point, some portions of the cloud 

 that had not been vaporized are converted into flakes of snow, 

 which act as nuclei to the hailstones. These flakes are quickly 

 surrounded by condensed water, which freezes into trans- 

 parent ice. The globules fall by their own weight from the 

 upper to the lower cloud, where they become recharged and 

 wetted. They are then attracted by the upper cloud, change 

 their electricity, and become reduced in temperature by radia- 

 tion and evaporation, and so acquire a new coating of moisture, 

 which freezes. They again return to the lower cloud, and thus 

 by a series of oscillations increase in volume until they become 

 too heavy for the attractive force of the electricity, and they 

 fall to the ground. 



Man\ of the objections urged against Volta's theory apply 

 also to Peltier's. But in matters of science the authority of 

 a great name is so potent that a false theory stamped with it 

 will retain its vitality long after its funeral obsequies have 



20 Brugnatelli's Giornale, x. p. 369. 21 Meteorologie, chap. xvi. 



