1872.] The Origin of the Great Cyclones. 419 
While philosophers and meteorologists, in many countries 
less favoured with a system of weather telegrams, have 
been discussing and disputing the reality of the law of 
storms, he sees it daily verified and is himself a storm warner. 
That ‘‘law,” first elaborated by Mr. Redfield and Col. 
Reid, simply stated, is this :—‘*‘ All gales or hurricanes are 
great whirlwinds, in which the winds blow in circuits 
around an axis vertical or inclined; that the winds do not 
blow in horizontal circles, but in sinuous spirals towards 
the axis, a descending spiral movement externally, and an 
ascending one internally, at the cyclonal centre; that the 
direction of apparent revolution is always uniform, being 
against the motion of the sun or against the hands of a 
watch turned face upwards, or from right to left in the 
northern hemisphere, and just the contrary in the southern 
hemisphere. The moment a barometric fall occurs, or, in 
any way, a sinking or depression of the atmospheric sea 
takes place, that moment, from all sides, the air begins to 
press inwards in radial lines upon the vortex. If the 
earth was not revolving on its axis, and the surface was 
smooth and polished so as to offer no friction, the air 
currents would flow in the direction of the spokes of a 
well-made wheel; on reaching the centre they would ascend 
as in a hollow and somewhat erect cylinder of air until they 
had restored the equilibrium of the agitated mass. The 
earth’s diurnal motion diverts them, however, to the right. 
Still they go forward to the centre of agitation, and, on 
reaching it, ascend. In ascending they grow cooler and 
cooler; their interstices grow smaller and smaller; their 
moisture is wrung from them at the altitude of a few 
thousand feet; and the evolution of the latent heat stored 
away in the vesicles of their aqueous vapour now begins, 
and the tempest begins to rage in earnest. This process 
goes on as long as the storm cylinder or centre is fed with 
the vapour of water, and, as we shall presently see, it 
ceases when that supply fails, as quickly and necessarily as 
the wheel or screw of the steamship ceases to revolve when 
her engineer cuts off the steam from her cylinders. 
Thus we behold the cyclonic meteor set in motion in- 
ternally from the circumference to the centre, simply by the 
formation of an atmospheric depression, and we see that 
internal motion—the air blowing in sinuous spirals upon the 
centre—prolonged, sustained, or intensified by the liberation 
of the latent caloric of aqueous vapour condensed into rain 
from the ascending air-current. 
From this philosophy of the cyclone—which, as far as it 
