GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
679 
These currents are shown distinctly by arrows in his diagram, notwithstanding 
some puzzling confusion introduced by lines which present the appearance of being 
meant to indicate average current lines, but which, in some parts, would suggest 
impossible courses, and which show signs of their having been put in without deli¬ 
berate care. Fig. 5 here is a copy of that diagram.* 
The diagram retains two vestiges of his original scheme. Thus it exhibits distinctly 
a depression of the top of the atmosphere at the Equator making a place of minimum 
height for the atmosphere there ; and it retains systems of arrows throughout the 
polar regions representing winds having, relatively to the Earth’s surface, motion 
Fig. 6. 
FERREL-1 889. 
N 
towards the west together with motion towards the Equator; and so in the polar 
region of the northern hemisphere representing north-east winds. Both of these 
features I regard as having been introduced through mistaken apprehension. In a 
later work, indeed, by Mr. Ferrel, entitled, ‘ A Popular Treatise on the Winds,’ 
1889,f both these features of his former scheme of circulation are completely 
eliminated from his scheme and theory as there presented. This is shown by his 
diagram^ taken in connection with the printed explanations by which it is accom 
panied. Fig 6 is a copy of this diagram. The depression of the top of the atmosphere, 
or more strictly speaking, the depression of any isobaric interface in the very lofty 
* The same diagram exhibiting his scheme of the winds is repeated in a subsequent paper by Ferrel 
of date 1861, which he offered as being more popular and less mathematical. It is to be found reprinted 
in ‘ Professional Papers of the United States Signal Service,’ No. XII. 
f London, Macmillan and Co. 
J Ferrel’s ‘ Popular Treatise on the Winds,’ 1889, § 105, p. 155. 
