ow
takes place? The atmosphere is differently estimated, at from thirty to
forty-five miles, or more, in height. Whatever its height may be, it is
exceedingly attenuated in its "upper regions."

Gay-Lussac marked the barometer at 12-95/100 inches at the height of
23,040 feet. Two thirds of the atmospheric density, then, is within five
miles of the earth. Air, too, is _compressible_. Allowing for the latter
and the attenuation, how many miles in vertical depth, of its "_upper
regions_," must move from one portion to another, to depress the barometer
two inches--its range sometimes in twenty-four hours--or even half an
inch? Let the computation be made, and see how startling the proposition,
how utterly impossible that the theory can be true.

The distinguished Professor, in the paper referred to, introduces his
theory of the formation of hurricanes, and we quote--

"If we suppose the upper portions of the air ascending over Asia and
Africa to flow off laterally, and if this takes place suddenly, it
will check the course of the upper or counter-current above the
trade-wind, and force it to break into the lower current.

"An east wind coming into a S. W. current must necessarily occasion a
rotatory movement, turning in the opposite direction to the hands of
a watch. A rotatory storm, moving from S. E. to N. W., in the lower
current or trade, would, in this view, be the result of the encounter
of two masses of air, impelled toward each other at many places in
succession, the further cause of the rotation (originating primarily
in this manner) being that described by me in detail in a memoir 'On
the Law of Storms,' translated in the 'Scientific Memoirs,' vol. iii.
art. 7. Thus, it happens that the West India hurricanes, and the
Chinese typhoons occur near the lateral confines on either side of
the great region of atmospheric expansion, the typhoons being
probably occasioned by the direct pressure of the air from the region
of the trade-winds over the Pacific, into the more expanded air of
the monsoon region, and being distinct from the storms appropriately
called by the Portuguese 'temporales,' which accompany the out-burst
of the monsoon when the direction of the wind is reversed."

The analogy between this, and a theory of Mr. Redfield's, will be noticed
further on. But I remark, in passing, that there is not a fact or
i