GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
675 
the Earth retarded with reference to the rapid whirl or vortex motion from west to 
east of the great mass of air above it, tends to flow towards the Pole, and actually 
does so flow under the indrawing influence of the partial void in the central parts of 
that vortex, due to the centrifugal force of its revolution. Thus it appeared to me 
that in temperate latitudes there are three currents at different heights :—That the 
uppermost moves towards the Pole and is part of a grand primary circulation between 
Equatorial and Polar Regions ;—that the lowermost moves also towards the Pole, but 
is only a thin stratum forming part of a secondary circulation ;—that the middle 
Fig. 4. 
THOMSOH - 1857. 
current moves from the Pole and constitutes the return current for both the pre¬ 
ceding ;—and that all these three currents have a prevailing motion from west to east 
in advance of the Earth. This was the substance of the new theory which I framed 
and which, in 1857, I submitted to the British Association at its Dublin meeting. 
The atmospheric currents supposed under this theory are indicated by arrows in the 
diagram, fig. 4, and may be traced out readily on inspection. This drawing it is to 
be understood is not intended to offer any indications of supposed variations in 
height from bottom to top of the atmosphere in different latitudes. 
I exhibited a,t the meeting, as an illustration, a simple experiment easily extem- 
4 r 2 
