Strictures on Dove's Essay "On the Law of Storms.'''' 141 



density of the air in regions so elevated is only one half of that 

 upon the earth's surface, is it conceivable that a whirlwind could 

 consist of materials so disproportioned in weight ? 



112. Can the suggested process of circulation proceed when, 

 in order for the lower stratum to exchange places with the upper, 

 it would have to move nearly half of the circumference of the 

 storm, or more than five hundred miles ? 



113. It has been shown that the rotating cylinder of air which 

 constitutes a hurricane, agreeably to the language employed, and 

 the theory espoused by Prof. Dove, may consistently with the 

 observed dimensions of storms, have a diameter two hundred 

 times as great as its altitude. The base, of this flat cylindrical 

 aeriform mass, must be in contact with the terrestrial surface, and 

 of course in collision with its ruggosities and inequalities, while 

 all the rest of the rotating superficies, being contiguous to inert 

 particles of the atmosphere, must incessantly share with them 

 any received momentum. Is there any known cause of motion 

 in nature, which can impart to a fluid and elastic mass so formed, 

 composed and situated, the various velocities necessary to that 

 simultaneous rotation of the whole which the creation of a whirl- 

 wind requires? In answering this question, it should be recol- 

 lected, that the velocities must diminish from the zones of which 

 the gyration is most rapid, towards the axis on one side, towards 

 the circumference on the other. 



114. Evidently no transient impulses can produce harmonious 

 revolution throughout the mass, unless they act upon every par- 

 ticle so as to impart to each the peculiar velocity which its dis- 

 tance from the axis may require ; and any enduring cause ope- 

 rating partially, could only affect the whole by a gradual process 

 of participation which would cause it to be expanded beyond as 

 well as within any " rotating cylinder''' which might be created. 



115. But admitting that in such a mass, under such circum- 

 stances, the gyratory violence of a hurricane could be induced, 

 could this violence be sustained, after the cessation of the gene- 

 rating forces, merely by the rotatory momentum of an enormous 

 aeriform disk, formed, proportioned, supported, and surrounded as 

 the whirlwind above imagined must be, could any such exist ? 



116. One of the grounds taken by Prof. Dove, appears to me 

 strikingly untenable. His language, Vol. in, p. 214, last para- 

 graph, is as follows. " The dead calm, suddenly interrupting 



