" On the Laio of Storms." 97 



the square of the distance from the axis. (See Additional Ob- 

 jections to Redfield's Theory, par. 82.) 



112. Professor Dove has not considered the incompetency 

 of a local cause of deflection to beget permanency of rotation 

 in a travelling storm; nor the impossibihty of the endurance 

 of a momentum sufficient to cause the violence of hurricanes 

 without continuous exciting forces. 



113. In a passage which I shall in the next place quote, the 

 idea is advanced that the axis of a whirlwind may incline for- 

 ward so as to cause the higher portion to precede the lower, 

 and to make the lower stratum of the air forming the whirl 

 exchange places with the upper stratum. This view of the 

 phaenomena I shall endeavour to prove erroneous. 



114. In Taylor's Scientific Memoirs, already cited, vol. iii. 

 p. 215, paragraph 3, Professor Dove has thus expressed 

 himself: — " In considering the progressive advance of the 

 whirlwind, we have not hitherto taken into account the re- 

 sistance opposed to the motion of the air by the surface of the 

 earth. 1 his resistance, as Redfield justly remarks, causes the 

 rotating cylinder to incline forward in the direction of its ad- 

 vance, so that at any station the whirlwind begins in the higher 

 regions of the atmosphere before it is felt on the surface of the 

 earth, where therefore the sinking of the barometer indicates 

 its near approach. The inclined position of the axis causes a 

 continual intermixture of the lower and warmer strata of the 

 air with the upper and colder ones, thereby occasioning heavy 

 falls of rain and proportionably violent electric explosions." 



115. In order to appreciate the fallacy of the ideas above 

 presented, it should be recollected that the *' rotating cyliiider " 

 of air, which is represented as inclining forKsoard^ can receive 

 this name only because the portion of the atmosphere of which 

 it is imagined to be formed, is conceived to revolve within that 

 cylindriciil space which must of necessity be occupied by a 

 whirlwind. To justify this appellation, the gyrating particles 

 must all move in concentric circles about a common axis, and 

 between planes parallel to each other and at right angles to 

 that axis. Any other rotative position of the parts must be 

 inconsistent with enduring rotation, since it would bring dif- 

 ferent parts of the mass in collision with each other and with 

 the air beyond the sphere of the gyration. It should be re- 

 collected also, that agreeably to observation, hurricanes have 

 been estimated to extend from 100 to 600 miles in breadth. 

 Let us assume the diameter of a whirlwind storm of this kind 

 to be 360 miles. Of course the circumference being about 

 three times as great would have three miles for every degree. 

 It follows, that a vertical circle of the diameter of the storm, 

 in a plane coinciding with the axis, would also have three miles 



Phil Mag. S. 3. Vol. 25. No. 164. August 1844. H 



