330 Proceedings of the British Association. 
deduced from the numbers given by Poisson, that it was much 
greater; that a cloud would be colder and not hotter than the 
surrounding air, and therefore the violent ascending vortex calcu- 
lated upon by Mr. Espy would not exist. Prof. Forbes had three 
objections to Mr. Espy’s theory: ist. the small funnel at the 
_ centre of a tornado, through which Mr. Espy supposed the air to 
rise, would be insufficient to vent all the air which would rush 
during a tornado, with the frightful velocity we know it to attain, 
through the constantly enlarging rings surrounding that central 
funnel, to the extent of many hundred miles. 2. As the tornado 
had a progressive motion, as Mr. E. admitted, it would be more 
difficult than Mr. E. supposed to deduce from the way in which 
the trees in its path were thrown, the actual course of the atmos- 
pheric particles at any instant, as each would move with a mo- 
tion compounded of. two motions, both varying in relative direc- 
tion and magnitude. 3. All the vapor in the air would be con- 
densed into cloud much sooner than Mr. E. supposed, and he 
thought it certain that the small amount of heat given out by the 
vapor would not suffice to expand the air in the funnel to the 
extent required, if Mr. Espy’s views were correct. As to the 
question whether Mr. Redfield’s and Col. Reid’s theory of a whirl, 
or Mr. Espy’s radial theory, was most- accordant with fact, Mr. 
Osler said, that from the investigation he had given this subject, 
he was convinced that the centripetal action described by Mr. Bb. 
took place in most hurricanes. The particulars which he, (Mr. 0.) 
had collected, together with the indications obtained from the 
anemometers at Birmingham and Plymouth, satisfied him that the 
action of the great storm of January 6 and 7, 1839, was not T0- 
tatory at the surface of the earth, whem it passed across England. 
He differed, however, both from Mr. Espy and Mr. Redfield in 
one essential point, for he believed it would be almost impossible 
to have a violent hurricane withont, at the same time, having 
both rotatory and centripetal action, A storm might very probably 
be generated in the first instance in the manner accounted for by 
Mr. Espy, or by the action of contrary currents: in the first case 
the rush of air toward a spot of greater or less diameter would 
not be perfectly uniform, owing to the varying state of the sur- 
rounding atmosphere ; this together with the upward tendency 
of the current would, in some cases, produce a violent eddy or 
rotatory motion, and a whirlwind of a diameter varying with the 
