Professor Olmsted's Reply to Dr. Christie. 373 



Art. XXIII. — Reply to Dr. Christie on Hail Storms ; by Denison 

 . Olmsted, Professor of Mathematics and Natural Philosophy in 

 Yale College. 



To the Editor of the American Journal of Science. 



Dear Sir, — In the JVew Edinburgh Philosophical Journal* is an 

 article on " Indian Hail Storms," communicated to that Journal by 

 A. Turnbull Christie, M. D. The writer mentions several facts 

 relative to the occurrence of hailstorms in the southern parts of India, 

 and of course within the limits of the torrid zone, which facts appear 

 to him inconsistent with the views I had offered respecting the causes 

 of hailstorms, in an article first published in the eighteenth volume of 

 this Journal, and republished in the New Edinburgh Philosophical 

 Journal. 



These facts are of so interesting a nature, that I could not wish 

 them to be witheld from your readers, although they should subvert 

 the explanation I had ventured to suggest; but whether they subvert 

 or confirm that explanation, your readers will have an opportunity of 

 judging, if they will do me the favor, after reading the annexed arti- 

 cle, to peruse the subjoined remarks. The article is as follows. 



[From the New Edinburgh Philosophical Journal.] 



On Indian Hailstorms ; by A. Turnbull Christie, M. D. 



In the last number of your Journal a new theory of hailstorms is 

 proposed by Professor Olmsted of Yale College, viz. that they are 

 caused by "the congelation of the watery vapor of a body of warm 

 and humid air, by its suddenly mixing with an exceedingly cold wind 

 in the higher regions of the atmosphere." 



According to this theory it is very easy to account for those hail- 

 storms which so frequently occur in some parts of the temperate zones, 

 as in the south of France, or in the United States of America; for in 

 such situations it is very possible that an intensely cold wind, pro- 

 ceeding from the north at a great height, might meet with a warm 

 body of air highly charged with moisture, and thus cause a very sud- 

 den congelation, with the other phenomena that generally accompany 

 such storms. But this explanation could not apply (even according 

 to the Professor's own showing) to hailstorms in the torrid zone, for 

 any two currents of air^ within this zone, would differ so little in tem- 



* This number of that work not having yet reached us, the above extract is taken 

 from the Philadelphia National Gazette, of June 14. 



Vol. XX.~-No. 2. 48 



