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SECOND REPORT — 4832 . 
were easy to multiply objections to this hypothesis, and some of 
the reasonings of the author relative to the production of cold are 
almost certainly erroneous ; but at the present moment it would 
be difficult to point out any explanation more plausible*. 
From the rarity of the occurrence of hail storms in this 
country, the subject has met with little attention compared to 
what it has received in most parts of the Continent f. In 
our Indian territories, however, the finest opportunities occur 
for the investigation of facts connected with the subject. Dr. 
Turnbull Christie has recently published, on this subject J, a 
short notice in reply to some theoretical views of Prof. Olmsted, 
an active American meteorologist §. We hope that among the 
scientific objects which engage Dr. Christie’s attention since 
his recent return to India, this will not be forgotten. 
This question has appeared of so much importance and in¬ 
terest on the Continent, that the Academy of Sciences at Paris 
has recently proposed the theory of hail as the subject of a 
prize memoir. 
Before concluding this Report, I am anxious to advert to the 
very interesting subject of the Aurora Borealis, —one which 
appears intimately connected with the science of Electricity, 
and upon which we cannot but hope soon to acquire new and 
extended views. 
I shall not dwell for a moment upon older observations, but 
proceed to state that Mr. Dalton has been led, from numerous 
and very interesting observations which he has collected upon 
auroral arches, to conclude that their average height above the 
surface of the earth is about 100 miles ||,—a conclusion not 
differing much from what he had long before been led to € f[. 
The frequent occurrence of these beautiful phenomena of late 
years, has rendered them an object of general observation, 
and many descriptions have been published by different authors 
in the periodical works of the day. The one of which Mr. 
Dalton deduced the height in the most satisfactory manner, was 
that of the 29th March 1826. The most striking examples 
which have since occurred, were on the 29th Sept. 1828, and 
the 7th Jan. 1831**. The last is perhaps the most extensively 
observed on record. 
* See on this subject a paper by M. Arago in the Annuaire for 1828. 
■j- See however an interesting account, by Mr. Neill, of a remarkable bail 
storm which occurred in Orkney some years since. Edinburgh Transactions, 
ix. 187. X Edinburgh New Philosophical Journal. 
§ Published in Sillimans Journal , 1830. [| Phil. Trans. 1828, p. 291. 
H In his Meteorological Essays. 
** On the last may be consulted papers by Mr. Christie, Mr. Harris, and 
