GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
G71 
understood. It is to be understood that the diagram shows a hemisphere of the 
surface of the Earth with the two Trade Wind Zones exhibited one on each side of the 
Equator, and separated by the Equatorial Belt of Calms and Rains, which is often also 
called the Doldrum Belt. And that it also shows the two Border Belts, or Calms of 
Cancer and Capricorn; and also, in the Northern Hemisphere, the zonal region of 
wind prevailing from south of west, and, in the Southern Hemisphere, the corre¬ 
sponding zone of prevalent winds from north of west. The arrows shown on the 
surface of the globe throughout these various zones indicate the directions of motion 
of the bottom currents of the atmosphere constituting the winds blowing on the 
surface of the sea. Around the representation of the globe the atmosphere is shown 
in section with arrows to indicate the north and south, and up and down motions in 
the circulation, which has just now been described in words. 
In offering this scheme of atmospheric circulation, Maury himself, in respect to the 
part of it which he propounds as taking place in the regions between the Trade Wind 
Zones and the Poles, confesses that it is “ for some reason which does not appear to 
have been very satisfactorily explained by philosophers ” that the currents he 
supposes do take place instead of their contraries. In short, he admits that he does 
not think reason has been found why in those regions the lower current should be 
towards the Pole and the upper towards the Equator, instead of what we might more 
obviously expect—namely, a flow towards the Pole in the upper regions of the 
atmosphere, and a return current towards the Equator in the lower regions close upon 
the surface of the sea. He even describes the known prevalent motion of the bottom 
layers of the atmosphere towards the Pole in extra-tropical latitudes as being 
seemingly paradoxical as to its reason, and although he offers an argument for 
abatement of the paradox, that argument on the slightest consideration may readily 
be seen to be futile. 
In 1856 — the year following after the publication of Maury’s scheme of circulation 
in his book entitled ‘ The Physical Geography of the Sea ’—quite a new theory was 
put forward by Ferrel in a paper on “ The Winds and the Currents of the Ocean,” 
published in the ‘Nashville Journal of Medicine and Surgery.’* The scheme of 
circulation which he then proposed and upheld by mathematical reasonings is illus¬ 
trated in his paper by a diagram, from which fig. 3 here is taken as a copy. This 
scheme, as may be noticed by reference to the diagram, and as may be further 
ascertained by reference to the original paper, includes for each hemisphere three 
zonal rings of atmosphere, making six in all, each having a separate circulation for 
itself, except that some small amount of commingling would necessarily take place at 
each narrow annular interface of meeting between two contiguous zonal rings. For 
either hemisphere one of these zonal rings of atmosphere covers the trade-wind region 
* October and November, 1856. This essay is to be found reprinted in ‘ Professional Papers of the 
U.S.A. Signal Service,’ No. 12, published by authority of the Secretary of Wai’, Washington, Office of 
the Chief Signal Officer, 1882. 
