Proceedings of the British Association. 331 
cause would ensue ; the centripetal action would thus be im- 
mensely increased, the whirlwind itself 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 
aheavy 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 rivat 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- 
tents 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, itmust. be considerable. Without embracing either theory, 
he thought it difficult to conceive, as he understood Mr. O. to do, 
‘te motion of rotation to be the primary, and the centripetal, 
(which indeed would be centrifugal,) force to be the secondary 
tenomenon. But it was comparatively easy to suppose the cen- 
‘Mpetal motion to be the primary phenomenon, and quite certain 
that if so; there must result a secondary phenomenon of rotation, 
of which indeéd some indications appeared in Mr. Espy’s maps. 
"making some remarks on the preceding paper, Sir D. Brewster 
observed, that it was impossible to form any decided opinion on 
Subject from the great want of well ascertained facts; and 
*s Mr. Espy had: founded his theory expressly on observations, 
often made by himself, it was impossible to do justice to his in- 
8enious views until a greater number of facts had been collected. 
