GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
669 
To account for the component from the south in these westerly winds of our 
middle latitudes, it came to be supposed, for instance, by Leopold yon Buch # 
prominently, as also by many others, that the air departing for the northern 
hemisphere from the top of the Equatorial Belt of buoyant air, while flowing north¬ 
ward still in the lofty regions of the atmosphere and over the Trade-wind zone, soon 
becomes a current from the south-west, and continues after descending to the Earth’s 
surface at the northern border of the trade-wind region still to move forward in 
continuation of its old course as a current from the south-west. But why in the 
lower regions a pole-ward motion should be maintained rather than a return flow 
towards the Equator, and how the return from higher to lower latitudes to com¬ 
pensate for this supposed pole-ward surface current should be accomplished, are 
questions which appear to have been scarcely mooted or to have been left enshrouded 
in vagueness. 
Many examples might be cited indicating the wide currency which such conclusions 
attained to, but one or two may suffice. Thus, for instance, in Johnston’s 
‘National Atlas,’ of date 1843, we have a map of the winds by Dr. Heinrich 
Bercihaus, of Berlin, on which the zone of south-westerly winds of middle latitudes 
is described in mysteriously poetic words more captivating to the imagination than 
satisfying to the reason, as “ Region of South-Westerly Currents of Air, or of the 
downward returning North-Eastern Trade Wind in Triumphal Conflict with the 
Northern Polar Currents .” 
Herschel, in his ‘Astronomy,’! of date 1850, gives an account for explanation of 
the south-west winds of middle latitudes substantially to the same effect as that of 
Leopold yon Buch and Berghaits, and with like vagueness as to the return 
currents from higher towards lower latitudes. 
But from the shelter of that prevalent vagueness, Maury, in 1855, stepped out and 
boldly offered a scheme of the general currents of atmospheric circulation which he 
supposed to prevail, in courses extending from Pole to Pole, and traversing in 
different ways the lower regions of the atmosphere next the surface of the Earth, and 
the upper regions which present themselves less directly to the observation of men. 
Fig. 2 is a copy of his diagram which, in conjunction with his printed explanations, 
sets forth his scheme of supposed circulation .| 
That figure shows a hemisphere of the Earth’s surface taken from Pole to Pole. 
* Leopold ton Buch, ‘ G-esammelte Scliriften,’ vol. 3, Berlin, 1877, where there is to be found his 
‘ Physikalische Beschreibung der Canarischen Inseln,’ Berlin, 1825, chapter 2, ‘ Bemerkung iiber das 
Klima der Canarischen Inseln,’ pp. 288, 289, and 290. A slightly abbreviated translation of the passage 
in question is given in Dove’s ‘ Law of Storms,’ Scott’s translation, 1862, p. 39, in a chapter entitled 
“ The Upper Return Trade Wind.” 
f Third edition. 
f Maury’s ‘ Physical Geography of the Sea.’ The first and second editions appeared in 1855. The 
statements here made apply alike to his 2nd and 6th editions, and presumably also to other editions. 
