56 Meteorological Sketches. 
as is known, thus commences at the lower extremity of the whirling 
mass or column, and the condensed and frozen drops, passing into 
Jayers of air of a temperature alternately above and below the freez- 
ing point, are carried upward by the powerful whirling and ascend- 
ing action of the vortex, till, with the successive coatings of con- 
densation received, they are finally discharged into the cold stratum 
at the upward extremity of the vortex, owing to the reduced tem- 
perature of which, they are prepared to receive a renewed acces- 
sion during their fall to the earth; or perhaps by their accumulated 
weight they are sometimes thrown through the sides of the vortex 
before reaching its higher extremity. By this violent whirling and 
elevating action, some of the hail-stones are thrown against each 
other and broken; and each successive layer of congelation may 
often be seen in the fractured sections of the hail. In all vorticular 
condensations of this character, when the cold is not sufficiently in- 
tense to produce hail, drops of rain are produced of a much greater 
size than are ever found in acommon and direct fall of rain. 
Hail storms of this character are less frequent in the tropical re- 
gions than in the temperate latitudes, for the reason, probably, that 
a stratum of sufficient cold to produce the hail, is seldom found so 
near the lowest stratum that a vorticular communication can be es- 
tablished with the former, by means of an ordinary gust, spout, or 
whirlwind. Nor does this ordinarily happen in the temperate lati- 
tudes ; but only when the lower warm stratum becomes overlaid, in 
close’ proximity, by a stratum from a colder region; an event which 
is not unfrequent in most countries within the temperate latitudes. 
It commonly happens, therefore, that several hail storms of greater 
or less magnitude and violence, occur on the same day, or about the 
same period. 
Of Thunder Storms and Gusts. 
When a cold stratum or current of the higher atmosphere moves 
or rests upon a warm one which is next the earth, neither stratum, 
as such, can penetrate or displace the other. Nor can a sudden in- 
terchange or commingling take place between the masses or parti- 
cles of which these strata are composed, except by the slow and te- 
dious process of the successive action and convolution of single par- 
ticles, or small groups of particles, upon or around each other ; but 
if a communication or interchange between the two strata becomes 
established by means of the action of a gradually excited whirlwind 
