58 Meteorological Sketches. 
and continue for some time, great destruction may be expected to 
follow. ‘The path of these destructive whirlwinds is generally nar- 
row, and often but a few hundred yards in width. 
From the nature of the causes which we have before mentioned 
as being favorable to the occurrence of a thunder storm, it follows 
that many of these storms will be likely to occur on the same day, 
in different parts of the same country, as has been already remarked 
in the case of hail storms, with which they are often identical; and 
the writer has often found this to’ be true to a remarkable extent. 
The fatal accidents by lightning, in different parts of the country 
have often happened on the same days, and we have reason to 
believe that scores of tornadoes, hail storms, and thunder storms, 
have sometimes occurred on the same afternoon. It usually happens 
that the precipitations of colder atmosphere at these numerous points 
of disturbance, are sufficient to produce a marked change in the tem- 
perature of the surface stratum within a period of twelve hours there- 
after. aie 
Atmospheric disturbances of this kind, which do not produce vio- 
lent thunder or hail, are usually denominated squalls ; and it appears 
highly probable that the presence of air of a temperature consider- 
ably above the freezing point, is necessary to the production of 
thunder and lightning. In the Strait of Magalhaens, in Patagonia, 
where the air at the surface is neither warm nor very cold, the 
squalls, called by the sailors williwaws, are very frequent, and tre- 
mendously severe ; but, according to the observations of Capt. P. 
P. King, lightning and thunder are seldom known. 
The heavy condensation presented in a thunder cloud, is often 
spoken of in a manner which implies that the cloud possesses some 
mechanical or other energy, by means of which the violent wind is 
sent forth; but nothing can be more unreal than such a supposition. 
_ The cloud may indeed be the means of electric development, and 
furnishes also the watery deposition for the hail or rain, but all the 
particles of the cloud are passively inert, like those of a common fog 
or mist, and the violent winds and disturbing forces which may be pres- 
ent, operate to produce the cloud, but do not, in any important 
sense, result from its action. 
Water-spouts and Whirlwinds. 
The character of these meteors has already been described, in a 
measure, in our account of hail and thunder storms. The identity 
