380 



The Great Wiltshire Storm. 



advances us only a little way in explanation of the back and side 

 currents, driving objects across and in the teeth of tbe general 

 course of the gale, and is not sufficient to account for tbe more re- 

 markable results of the storm. Now no one seems to me to have 

 given so probable a solution to this mystery, (and certainly no one 

 has made such deep researches and investigated so diligently the 

 whole theory of storms) as Mr. Rowell. He states in one of his 

 publications on the subject, 1 after some very masterly arguments 

 and a chain of proofs in support of his opinion, " that tbe vacuum 

 or rarefaction created by the fall of rain and the escape of its elec- 

 tricity is the cause of storms and tornadoes of all kinds, on the 

 theory that particles of vapour are carried up and supported by 

 tbeir coatings of electricity ; and as water is 860 times heavier than 

 air at the sea-level, and as each particle must occupy the space of 

 an equal weight of air, it follows that on the fall of an inch of rain 

 a vacuum or rarefaction would result in the space above, equal to 

 that which would be produced by tbe abstraction or annihilation 

 of 645 cubic feet of air over every square yard where such rain 

 might fall, and during the time in which it was falling;" and 

 again, that when portions of a cloud are attracted towards the 

 earth, or when heavy rain falls, a vast conductor is thus formed 

 " for the accumulated electricity of the cloud to the earth ; then 

 as the passage of electricity is so instantaneous, an enormous va- 

 cuum or rarefaction would be produced within the cloud, on the in- 

 stant of the passing off of the electricity: matters beneath the 



against the theory I advance still I cannot say that I could see any evidence of 

 a whirlwind in it, and I helieve that the position of the trees that fell (as far as 

 I saw them) may be accounted for, either from a rush of air right onward into 

 the rarefied space produced by the passing of the storm cloud, or by an occa- 

 sional lateral rush of air from the northward or southward, but chiefly from 

 the latter. A man in answer to my question of how the rain seemed to fall, 

 said, "it came down in swashes," and I think it may also be said that 

 occasionally the wind came in swashes too. The effect of the wind on the lea- 

 side of houses, &c, gives no evidence of a whirlwind, as I think it may be 

 oaused by the rarefaction of the air being more complete on the lea-side than on 

 the windward of a building as the clouds passed over, and I think that the lateral 

 rush of air into such spaces would produce such effeots as those I saw." 



1 See Mr. Rowell's very able Essay "On the cause of rain and its allied 

 phenomena," (Oxford, 1859) which will well repay a careful perusal. 



