The Philosophy of the Weather. And a Guide to Its Changes

by T. B. Butler

“The whole experiment serves to demonstrate that such an active gyration as we have ascribed to storms, and have proved, as we deem, to appertain to some, at least, of the more violent class; must necessarily expand and spread out, by its centrifugal action, the stratum of atmosphere subject to its influence, and which must, consequently, become flattened or depressed by this lateral movement, particularly toward the vortex or center of the storm; lessening thereby the weight of the incumbent fluid, and producing a consequent fall of the mercury in the barometrical tube. This effect must increase, till the gravity of the circumjacent atmosphere, superadded to that of the storm itself, shall, by its counteracting effect, have produced an equilibrium in the two forces. Should there be no overlaying current in the higher regions, moving in a direction different from that which contains the storm, the rotative effect may, perhaps, be extended into the region of perpetual congelation, till the medium becomes too rare to receive its influence. But whatever may be the limit of this gyration, its effect must be to depress the cold stratum of the upper atmosphere, particularly toward the more central portions of the storm; and, by thus bringing it in contact with the humid stratum of the surface, to produce a permanent and continuous stratum of clouds, together with a copious supply of rain, or a deposition of congelated vapor, according to the state of the temperature prevailing in the lower region.”

The italics in the foregoing extract are mine; and, in relation to it, I observe:

1st. There is no cylindrical vessel around storms, and air will not thus resist air. Confessedly, such resistance is necessary. Let any one watch his cigar smoke, and see how readily it moves on, with little momentum. Let any one try the experiment of creating a whirl in the open air, or in a room, or box of paper, or other material, which can be suddenly removed, with air colored by smoke. I am exceedingly mistaken if he does not find the presence of a “cylindrical vessel,” absolutely essential to prevent the instantaneous tangential escape of the air.

2d. Turn back to page 3 and look at the fall of the barometer in the polar regions (recorded in the extract from Dr. Kane), with scarcely any wind, and as little variation in its direction, and see how utterly Mr. Redfield’s theory fails to account for the phenomena.

3d. If I understand Mr. Redfield correctly, he has abandoned the claim as originally made, that the wind moves in circles, expanding, and spreading out by a “lateral movement,” and now asserts that it blows spirally inward, and elevates the air in the center. I quote:

“Vortical Inclination of the Storm Wind.—By this is meant some degree of involution from a true circular course. In the New England storm above referred to, this convergence of the surface-winds appeared equal to an average of about 6° from a circle. In the present case, such indication seems more or less apparent in the arrows on the storm figures of the several charts, where the concentrical circle afford us means for a just comparison of the general course of wind which is approximately shown by the several observations.

“Perhaps we may estimate the average of the vorticose convergence, as observed in the entire storm for three successive days, at from 5° to 10°—out of the 90° which would be requisite for a congeries of centripetal or center-blowing winds. This rough estimate of the degree of involution is founded only on a bird’s-eye view of the plotted observations. But, however estimated, this involution seems to afford a measure of the air and vapor which finds its way to a higher elevation by means of the vortical movement in the body of the storm.”

If the elevation of the air at the borders of the storm, and depression in the middle, resulted from the outward tendency and “lateral movement” of the revolving air, and from the centrifugal force, as in the experiment with the water in a cylindrical vessel, as stated in the first paragraph quoted, an involution of from 5° to 10° from the action of a centripetal force, must carry the air inward, and the barometer should stand highest in the middle of the storm. The change is fatal to his theory. The two are diametrically opposite in character and effect. In one, the superior strata would be brought down in the center by the lateral pressure outward; in the other, they would be elevated by the involution, which “affords a measure of the air and vapor which finds its way to a higher elevation,” etc. It is perfectly obvious Mr. Redfield has refuted his own hypothesis.

In doing this, he is met by the other difficulty alluded to, which he does not attempt to explain. This gathering of the air inward, spirally, by a centripetal force, if it took place, not only would not depress, but must elevate the barometer in the center, above that of the adjoining atmosphere.

When he first attributed the depression of the barometer to a lateral movement and centrifugal force, he supposed the superior strata descended into the depression, and their frigidity occasioned the condensation, and cloud, and rain. How he now proposes to account for the formation of cloud and rain during storms, while the warm air of the inferior stratum finds its way to a higher elevation in the center of the storm, he does not inform us, and we must wait his time.