But there is another principle which modifies these effects. We have
already adverted to the action of the tangential current of the vortex
forcing the outer layers of the atmosphere into waves. These waves will
be interfered with by the different vortices, sometimes being increased
and sometimes diminished by them.[6] If these waves are supposed very
wide, (which would be the case in the attenuated outside layers of the
atmosphere,) the action of the vortex will be greater in its passage
over a place, which at the time corresponded to the depression point of
the wave, that is, to the line of low barometer; because here there
would be less resistance to overcome in the passage of the ether from
the surface of the earth into space; so that we may conceive each vortex
making a line of storms each day around the earth, separated by less
disturbed intervals. After the formation of the storm, it of course has
nothing to do with the vortex that produced it; it travels in the
general direction of the local atmosphere of the place--in intratropical
latitudes westward, in extratropical latitudes eastward. If, therefore,
the disturbance forms at the place of observation, there will probably
be no storm; but further eastward its action would be more apparent or
violent. It is impossible, of course, to lay down any general
description which shall meet every case. It is a knowledge that can only
be acquired by observation, and then is not readily or easily
communicated. There are many contingencies to be allowed for, and many
modifying causes to keep sight of, to enter into which would only be
tedious; we shall, therefore, confine ourselves to the prominent
phenomena.