Proceedings of the British Association. 331 



cause would ensue ; the centripetal action would thus be im- 

 mensely increased, the whirlwind ^7se//* demanding a vast supply 

 of air, which would be constantly thrown off spirally upwards, 

 and diffused over the upper atmosphere, thus causing the high 

 state of the barometer which surrounds a storm. He further 

 stated that he had brought his theory of the combined action of 

 centripetal and rotatory motion before the meeting at Birming- 

 ham, and a short notice of it would be found in the reports of 

 the Sections. If no rotatory action takes place, he believed that 

 we merely experienced the rush of air which necessarily precedes 

 a heavy fall of rain or thunder storm ; but he believed that noth- 

 ing violent enough to be called a hurricane could take place, 

 unless a violent rotatory or whirling action be first produced, and 

 that in many and perhaps most cases, the rotatory portion is not 

 in contact with the earth. Mr. Arch. Smith said there was one 

 point which must not be overlooked in any correct comparison of 

 the rival theories. From the principle of the conservation of 

 areas it was perfectly certain, that if a storm was caused in the 

 manner supposed by Mr. Espy, there must be a rotation, greater 

 or less, in. the centre. Because, unless the motion of all the cur- 

 rents were accurately directed to one point, or at least their mo- 

 ments in a horizontal plane were equal to zero, which was infin- 

 itely improbable, a motion of rotation must be the result, as in the 

 instance of the motion of water in a funnel cited by Mr. Espy. 

 If the central space of comparative rest were large, the whirl 

 might be imperceptible ; but if small, as in the case of a water- 

 spout, it must be considerable. Without embracing either theory, 

 he thought it difficult to conceive, as he understood Mr. O. to do, 

 the motion of rotation to be the primary, and the centripetal, 

 (which indeed would be centrifugal,) force to be the secondary 

 phenomenon. But it was comparatively easy to suppose the cen- 

 tripetal motion to be the primary phenomenon, and quite certain 

 that if so, there must result a secondary phenomenon of rotation, 

 of which indeed some indications appeared in Mr. Espy's maps. 

 In making some remarks on the preceding paper, Sir D. Brewster 

 observed, that it was impossible to form any decided opinion on 

 the subject from the great want of well ascertained facts ; and 

 as Mr. Espy had founded his theory expressly on observations, 

 often made by himself, it was impossible to do justice to his in- 

 genious views until a greater number of facts had been collected. 



