114 Biographical Sketch of Prof. Olmsted. 
by him, in 1830, inthe American Journal of Science,—ascrib- 
ing their origin to the sudden mingling of large bodies of hot 
and humid air with air extremely cold, by which the vapor of 
the former would be rapidly condensed and congealed into hail; 
which effect would be produced whenever, by means of oppos- 
ing winds, whirlwinds, or other atmospheric disturbance, hot 
air should be carried above the line of congelation or cold air 
brought below it. This hypothesis, though it has never obtained 
the celebrity of the ingenious, but improbable, electrical theory 
of Volta, is yet, perhaps, as plausible as any, or at least is suffi- 
ciently so to warrant its author in his steady adherence to it, es- | 
pecially if we consider that such is the intrinsic difficulty of the 
subject as to compel the acutest physicists to confess that no 
satisfactory theory has yet been proposed,—hailstorms being 
characterized by Pouillet as among the most formidable of 
scourges to agriculture, and the most perplexing of phenomena 
to meteorologists. 
In respect to the great storms of our Atlantic coast, and simi- 
lar ones elsewhere, he adopted in the main, the rotary theory of 
Mr. Wm. C. eld, whom he early encouraged in the devel- 
opment of his views on this subject, and for whom he cherished 
a sincere attachment, which led him, after the death of his 
friend, to prepare the eulogium which he delivered before the 
American Association for the Advancement of Science, at its 
meeting in Montreal. In this address Prof. Olmsted thus defines 
is own position in respect to Mr. Redfield’s views. “ While 
from the first I have heartily embraced Redfield’s doctrine that 
ocean gales are progressive whirlwinds, and have further fully 
believed that he had established their laws or modes of action 
on an impregnable basis, a regard to truth and candor obliges 
me to say, that I have never been a convert to his views respect- 
ing the ultimate causes of storms, especially so far as he assigned 
for these causes what he denominates the ‘diurnal and orbitual 
motions of the earth,’ but his notions on this point have always 
appeared to me unsatisfactory.” ‘ 
he phenomena of the northern lights, such remarkable exhi- 
acelin ha 
Eg a 
assigning to the phenomena a secular period of about sixty oF 
sixty-five years. This vi owledged, 
} 
