by gyratory or circular ones. How are they
produced? This question can only be answered by analogy. No permanent
impressions are left by the circular currents, except to a limited extent,
and in occasional instances; and observation of them has been, and must
necessarily be limited and uncertain. I have witnessed one or two on a
moderate scale; but owing to the suddenness of their passage, and the
confusion of the objects taken up, it was difficult to determine what the
circular currents were. When the southerly current is much the strongest,
it appears sometimes to cross the axis, and curve round the northerly one.
Perhaps this may be all the curving that really takes place, except at the
posterior part of the axis, for evidence of a curving on the south of the
axis is rarely, if ever seen.

Assuming, however, that the main currents unite and form one from the
earth to the cloud, _induced_ circular currents would be in perfect
keeping with the known laws of electricity. Such currents, and with
magnetic properties, are always induced by powerful currents of voltaic
electricity passing through wires. And doubtless _in all cases_ powerful
currents of electricity _induce attendant circular currents_. This may
account for the external gyration of the spout.

Or it may be that the two lateral currents of air which attend the
currents of electricity, do not unite; having opposite polarity, but pass
by and around each other, in connection with the circular magnetic
currents. Future observation and perhaps experimental research will
determine this. But it may not be accomplished by the present generation;
for the belief that tornados are mere whirlwinds, produced by the action
of the sun in heating the land, is adhered to, notwithstanding they cross
the intense magnetic area of Ohio in mid-winter, and seems to be
ineradicable.

The proportions of different winds vary in different localities. For the
benefit of those who are curious, I copy a table from an able compilation
by Professor Coffin, published by the Smithsonian Institute, showing the
proportion of the winds at New Haven (the station nearest to me). It will
be noticed that during the year the N. W. winds blow the greatest number
of days; the S. W. next; the N. E. and S. E. less than either, and about
equal. It may be observed that the two latter bear about the same
proportion to the whole, that our number of cloudy and stormy days,
averaging about ninety, bear to th