THE BIRTH, LIFE, AND DEATH OF A STORM. 
245 
stages, and in which they fail to see evidence of the pre-exist- 
ence of two, and only two, determinate currents. 
Another serious objection to this theory is that it does not 
assign a vera causa sufficient to give the first impetus to the 
barometrical fall and the rotatory movement of the air. 
3. A third theory of the origin of these storms is that which 
is strongly urged by M. Faye, in Paris, and is to the effect that, as 
interfering currents in rivers give rise to vortices which extend 
from the surface downwards into the water, so all our water- 
spouts, trombes , and even the largest tropical hurricanes must be 
all formed in the upper regions of the atmosphere, and extend 
downwards to the earth : the force which gives them their on- 
ward motion being supplied by the upper currents. 
It is sufficient to say that this theory has not met with accep- 
tance from any practical meteorologist, while it is directly 
controverted by recent investigation into the motion of cirrus 
clouds, which show beyond a doubt that the motion of the upper 
currents of air over a cyclone is outwards, and not inwards, as 
the descending theory would demand. 
Moreover, some of our readers may have noticed in “ Nature ” 
of January 16, a notice, copied from the “ Times,” of the forma- 
tion on the Lake of Geneva, on January 2, of a veritable small 
water-spout, 40 feet high and 1 0 yards in circumference, by the 
meeting of two winds, known locally as the Fohn and the Bise , 
on the surface of the lake. Here the waterspout was raised, and 
did not descend from the clouds. 
4. The last theory we shall notice is that of the late Mr. 
Thomas Belt, who seeks for the origin of the disturbance on 
the ground, and, like M. Faye, assigns the same explanation to 
the smallest dust-whirl eddies and the largest storms which 
sweep over the earth. 
This theory assumes as the first cause the heat of the sun. 
The heat-rays pass through the atmosphere without warming 
the upper strata, and so Mr. Belt supposed that over a sandy 
soil a mass of air close to the ground might rise in temperature 
much higher than the superincumbent layers of the atmosphere. 
The lower strata would therefore become lighter, and a condition 
of unstable equilibrium would arise. This, however, could not 
last for ever, and, sooner or later, the heated lower air would 
burst up, and the ascending column thus produced would be the 
nucleus of the nascent cyclone. 
The difficulty in accepting this explanation is that we should 
like some ocular evidence of such a sequence of conditions. 
The supporters of the theory, however, point to accredited 
instances of the formation of whirlwinds over volcanoes like 
Santorin, and over extensive fires like those of Carolina cane- 
brakes. 
