106 British Association for the Advancement of Science. 



a whirlpool. The general correctness of this view was shown 

 by the fact that Mr. Redfield's and Col. Reid's whirls were found 

 to adv^ance along the course of the gulf-stream, the warmth of 

 which tended to load the air above it with vapor ; and in the hur- 

 ricane which did such damage to Charleston, the town was saved 

 from destruction by the fact that the most violent part of the 

 storm followed the bend of the river : the shipping was nearly 

 destroyed. In this way was also to be accounted for, the perplex- 

 ing fact that the storm was propagated against the course of the 

 wind, as is well known also in summer thunder storms. These 

 were the phenomena of dry storms. When much rain fell, the 

 space above was left arid also by the descent of the water, while 

 the air below was pushed out on all sides, thus very much modi- 

 fying the current at the surface, increasing the force to leeward, 

 and diminishing it to windward, causing sometimes the fearful 

 and sultry calm preceding the thunder storm ; the fall of tempe- 

 rature above, in consequence of the expansion of the air rushing 

 in to fill the void, often froze into hail the rain-drops as they 

 passed through, the surface of the boles of which would be clear 

 ice ; but, expanding as it formed the shell, the inner part would 

 be opake and crystalline, because partly void. Mr. Espy, of Phil- 

 adelphia, had a theory nearly the reverse of this : he conceived 

 the heat given out by the vapor in passing to the state of cloud 

 or rain, to be so abundant, as, by its rarefying influence to cause 

 a rapidly ascending column or vortex, capable of producing most 

 appalling effects ; and the only step doubtful in this theory was 

 the first, — for before the vapor can pass to the state of water, it 

 must be robbed of this very latent heat by an external cause ; but, 

 grant this first step, and the rest of Mr. Espy's theory was almost 

 a series of mathematical demonstrations. 



A valuable paper was then read, " on certain results which he 

 had recently arrived at, respecting the minimum thickness of the 

 crust of the globe, which might be consistent with the observed 

 phenomena of Precession and Nutation, assuming the earth to 

 have been originally fluid," by Mr. W. Hopkins. 



Mr. Smythies then communicated a general method of solving 

 dynamical problems relating to the motion of free bodies, by 

 means of differentiation and elimination of differentials without 

 any integration, by which the result is obtained in a finite number 

 of algebraical terms, when the equations of condition determin- 

 ing the motion are algebraically assigned. 



