Notices of Tornadoes, §c. jy » 83 
dance of puppets, or the vibration of a pendulum, or bell clapper. 
The passage of sparks is found to arrest or to check such move- 
ments, aud in like manner the passage of lightning has been ob- - 
served to mitigate the vertical force of a tornado. 
While a meteor of this kind, which passed over Providence 
last year, was crossing the river, the water, within an area of 
about three hundred feet in diameter, was found to rise up in a” 
foam, as if boiling. Meanwhile two successive flashes of light~ 
hing occurring, the foam was observed to subside after each flash. 
It is thus proved that a discharge by lightning, is inconsistent 
with the discharge by convection, and that so far as one ensues, 
the other is impeded. 
In an account of a tremendous storm of the kind of which I 
have been treating, published in Silliman’s Journal for July last, 
it is mentioned that at its commencement it was only a violent 
thunder gust. This is quite consistent with the experience ac- 
quired by means of our miniature experiments, in which a dis- 
charge by sparks may be succeeded by a discharge by convection, 
or Vice versa; or they may prevail alternately. In one case the 
electric fluid passes in the gigantic sparks called lightning, in the 
other it is conveyed by a blast of electrified air. In the former 
case, animals are subjected to deleterious shocks, while in the 
latter no other injury is sustained than such as results from col- 
lision with the air, or other ponderable bodies. 
In the case of the tornado, the vertical blast is accelerated by 
the difference between the pressure of the air at the earth’s sur- 
face, and at the altitude to which the blast extends. Should this 
be a mile there would be a difference nearly of one hundred and 
forty four pounds per square foot. During the tremendous gale 
which prevailed-at Liverpool last winter, the greatest pressure of 
the wind was estimated at only thirty pounds per square foot. 
So far as the ingenious inferences and observations of Mr. Espy, 
as to the buoyancy resulting from a transfer of heat from aqueous 
vapor to air hold good, the vertical force so alledged to arise, will 
co-operate to aid the influence of electric discharges by con- 
Vection. 
The distinguished author of the memoir alluded to at the out- 
set of this communication, conceives that were electricity the 
cause of tornadoes, the magnetic needle should be disturbed by 
them ; and without advancing any proof that such disturbance 
ee. 
