
TRANSACTIONS OF THE SECTIONS. 31 
riments of Mr. Joule have proved. This must cause an elevation of temperature, 
which will go on until the loss of heat by radiation, conduction, and evaporation 
balances the gain by friction, and at this point the temperature of the river will 
remain stationary. 

Meteorological Summary for 1851, at Huggate, near Pocklington. 
By the Rev. T. RANKIN. 
This, as usual, contained a summary for the year of the thermometer, barometer, 
hygrometer, rain-gauge, atmospheric waves, winds, aurore, and meteors observed 
at Huggate. It also contained a brief notice of eclipses. 
On an Aurora observed at Huggate. By the Rev. T. Ranxin. 
On the Aurora Borealis. By Rear-Admiral Sir Joun Ross. 
This explanation of auroras is the same as that which was formerly given by Sir 
John Ross at the Dublin Meeting in 1835. 
On the Formula for the Wet-bulb Thermometer. By Capt. STRACHEY. 
The author stated objections to the principle on which Dr. Apjohn’s formula 
had been investigated; affirmed that this formula was found not applicable to 
the high temperatures and dew-points observed in India, and proposed a correction 
in that part of the process which involves the difference of the number of degrees 
of the dry and wet bulbs. 
On Tropical Hurricanes. By Dr. J.. Taytor. 
The author began by stating the observed facts as to these hurricanes. They 
begin from 10° to 20° from the equator, but are not observed at it. A hot, sultry 
and calm state of the atmosphere, with a low barometric pressure, indicates their 
occurrence, or immediately precedes them. The force of the wind increases as the 
centre of the area over which the action of the hurricane extends is approached. 
The author then poizited out the inconsistency of the theory of Mr. Espy and other 
American philosophers with the facts observed, and particularly that a ship situ- 
ated in a Storm of the structure which that theory supposed would find the wind to 
bear in either direction indifferently in the northern or the southerh hemisphere; 
which is contrary to experience; for the direction of the whirl in the northern 
hemisphere is always contrary to the motion of the hands of a watch; while in the 
southern it was as constantly in the same direction for the true cyclone. He stated 
his conviction that the opinion which is alone consistent with all the facts is, that 
the movement of the air is one of revolution round a central space which is itself in 
a state of progressive motion; and that the direction of the rotatory movement is 
invariable in the same hemisphere. The author then sketched the causes which 
might give rise to such a rotatory movement; particularising the hypothesis of Dove 
and others, viz. that of contending currents, and showing its utter iricompetence ; 
and proceeded to give the theory which he proposed of them, viz. that the partial 
vacuum indicated by the low state of the barometer over the area of the storm, arid 
* particularly towards the vortex, is not the effect of centrifugal force, but the original 
cause of the movement, by inducing a translation of air from beyond the boundary of 
the partial vacuum inward towards its centre,—a motion which would occur in directly 
converging right lines were the earth and air at rest; but the earth being in motion, 
and therefore the area of the hurricane turning round with regard to its own centre, 
the velocity of such movement being greater for a particle of air at a distance from 
that centre than for one nearer, as the particles approach it, they retain their greater 
velocities, and thus move not in radial lines, but in diminishing circles or spirals 
round the centre, which would be the case were the particles of air only to retain 
their primitive velocity of rotation; but by the principle of the conservation of areas, 
the velocity would increase more and more as the centre of the vortex was approached. 
