390 The Iowa and Illinois Tornado. (July, 
The horse-power required to raise 5,330,020,875,922 lbs. 
to a height of 5 miles per minute amounts to— 
5,330,020,875,922 X 5 X 1760 x 3 
33,000 
= 4,264,016,700,737°6 horse- 
power. 
These figures convey a better idea of the tremendous 
power of the tornado than any mere verbal description 
could do. They also show that the power evolved by the 
condensation of vapour, while enormous, is by no means 
sufficient to supply the whole energy developed by the tor- 
nado. We must therefore look for another source of power. 
This is no doubt to be found in the destruction of the 
atmospheric equilibrium by an abnormally warm southerly 
current flowing under a much colder, and consequently spe- 
cifically heavier, stratum of air. 
In an extensive paper, which will be found in the Chief 
Signal Officer’s Annual Report for 1873, the author passes on 
to the consideration of the general atmospheric conditions 
under which the tornado originated. The length of this 
article, however, precludes our entering fully into this branch 
of the subject. 
The Electrical Phenomena must be regarded as. merely 
secondary. In the lofty centrifugal cloud there was inces- 
sant thunder and lightning; but very little, if any at all, in 
the centripetal cloud and the funnel. One obje¢t, a tree, 
was struck in the path of the storm, but the discharge took 
place half an hour before the arrival of the funnel. The 
lightning-rod said to have been melted on widow Dogget’s 
barn might have been struck long before, and only noticed 
then because it was blown down. 
There were no evidences of electrical action upon the 
trees, which were peeled and shivered by the storm, although 
there was that brown appearance when the trees were broken 
which has been referred to the action of electricity. This, 
however, was clearly due to the straining of the tree before 
it broke. 
No one saw any objects tipped with electrical light during 
the progress of the meteor. The telegraph was not inter- 
rupted until the wind blew down the wires. 
It is the generally-accepted opinion that in tornadoes 
houses are frequently burst asunder when the centre of the 
whirlwind comes over them. This is supposed to be accom- 
plished by the great rarefaction, which is said to exist in the 
centre, suddenly relieving the air within the houses of a large 
portion of atmospheric pressure. The air thus relieved of 
