GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
657 
to refer, is that of Dr. Garden of Aberdeen, which, about one year after that of Dr. 
Lister, was placed on record in the ‘ Transactions of the Royal Society.’ Dr. Garden, 
in his paper,'" attributes the east to west motion of the Trade Winds of the Atlantic 
and Pacific Oceans to the supposed vortices of a supposed ether, or all-pervading 
atmosphere, which, according to the planetary system proposed by Des Cartes, and at 
that period still believed in by some, were imagined to be the agents carrying on or 
sustaining the revolutions of tlie Planets round the Sun, and of the Moon round the 
Earth, and of the Earth round its own axis. Dr. Garden’s paper gives indication of 
his having some knowledge, not only of prevalence of winds from the east within the 
tropics, but also of prevalence of winds from the west in higher latitudes outside of 
the tropical regions. He gives no indication of knowledge of the Trade Winds having, 
along with their westward motion, also motions towards the Equator from both sides ; 
and is, in this respect, apparently on an equality with Dr. Lister. They had both 
made praiseworthy exertions in collecting and bringing into notice important results 
from the observations of mariners and other travellers. When, however, Dr. Garden 
offers explanations of his supposed reasons for the blowing from east to west within 
the Tropics, and from west to east in latitudes higher than those of the tropical regions, 
his statements, in their meaninglessness, quite transcend the inadequacy of the 
explanations in the amusing attempt of Dr. Lister. 
The papers of these two men may probably have had a beneficial effect in instigating 
Halley to prepare, for the Royal Society, a paper presenting the results of his 
researches as to the observable facts of the winds, and. his speculations to account for 
the prevalent directions of them motions. In 1G86, about one year after Dr. 
Garden’s paper, Halley, then at the age of thirty, submitted to the Society an 
elaborate and very clear account of the information as to the winds in different parts of 
the world which he could collect from numerous sources, including observations carefully 
made by himself on voyages and on land between the Tropics. The title of his paper 
in the ‘ Transactions,’ is “ An Historical Account of the Trade Winds, and Monsoons 
observable in the Seas between and near the Tropicks, with an attempt to assign the 
Physical Causes of the said Winds.”+ His description of the observed facts and his 
theoretical considerations on the subject, have constituted an important step in the 
development of the science of that subject, even though his theory in its most important 
part—that which relates to the east to west motion of the Trade Winds—turns out to 
be fundamentally untenable. He adduced, no doubt, in his explanation, an important 
part of the real truth as to causes of the wind, a part which, if not first suggested by 
him, was clearly either not generally known or not generally adopted at the time. 
This true element in his theory consisted in his assigning as the primary motive 
cause of the winds, the expansion of the air of hot regions, accompanied by its outflow 
in its upper parts from those regions towards places of less heat and entailing a 
* ‘ Phil. Trans.,’ vol. 15, No. 175. September and October, 1685. 
t ‘ Phil. Trans.,’ No. 183, p. 153. 
MDCCCXCIL—A. 4 P 
