* 
376 Professor Olmsted’s Reply to Dr. Christie. 
there is usually, if not always, a change of direction. in the wind ; 
that is, the wind blows from a different quarter after the storm, and is 
often exceedingly cold when the quantity of hail that falls is too ree: 
to. produce so great a change. 
‘Dr. Christie is under a mistake in supposing that my explanation 
of the causes of hailstorms, requires that these storms should never 
occur in the torrid zone, except in the region of high mountains. — 
So far from this, the theory demands that Ladeotite should occur 
wherever such hot and cold blasts of air, as he mentions, meet and 
mix together. For obvious reasons assigned in my paper, they ¢ do. 
not often meet in the torrid zone, and accordingly hailstorms are 
eat less frequent there than in the temperate zones. two 
very respectable authorities which I quoted,* inform us, the one that 
they never occur in the torrid zone, and the other that they are never 
met with, except at an elevation of one thousand five hundred. or two 
thousand feet. It appears, however, from’ the facts adduced in the 
foregoing article, that there are other situations within the torrid zone 
where hailstorms occur ; but’ still, so far as we cam gather the cir- 
cumstances from the briéf statements of Dr. Christie, these-storms 
result.from the same causes as were assigned for hailstorms in gener. 
al, namely, from the sudden meeting of blasts of very hag and very 
cold air. 
I beg. leave to add. one.remark more. Although I Lares endeav- 
ored to show the precise manner in which these hot and cold blasts 
meet, and hence, as [ suppose, furnished a probable explanation of 
the extraordinary fact, of the much greater frequency of hailstorms 
in the temperate, than in the torrid or the frigid zone, yet should 
blasts meet in any-other manner,—should cold and hot portions 
of air meet either by the subsiding of ‘cold strata from above, 25 _ 
maintained by Professor Mitchell,t or should the opposite kinds of 
winds be mixed. together in the form of whirlwinds, as maintained by 
Mr. Redfield,} the leading doctrine which I have advanced would still 
be true, that hailstorms result from the mixture of blasts of hot and 
cold air, and not from any agencies of electricity, to which wee have 
been more commonly ascribed. 
Respectfully and truly yours, 
Denison OLMSTED. 
» 
Yale College, June 17, 1831. 
— at ee 
& 
z ~* Rees’ Cyclopedia, and the Edinburgh por Sora 
| Amer. Jour. Vol. XIX $ Ebi 
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