GRAND CURRENTS OF ATMOSPHERIC CIRCULATION. 
G65 
Not only before, but also after this episode of Dalton’s speculations and researches so 
published, the theory of Hadley must certainly have remained but little read in its 
author’s original paper. 
Within the first half of the present century writings on the winds, including the 
Trade Winds and general circulation of the atmosphere, have been very numerous, 
some of these have appeared in our encyclopaedias, and others in works on meteorology 
and navigation, and have been widely diffused in atlases containing maps and charts 
on physical geography. 
In such ways many sketches have been presented to the public as explanations of 
the Trade Winds and other currents of the atmosphere related to them, embodying 
more or less of the fundamental principles of Hadley’s theory, but often without 
reference to his name, and usually without due appreciation of the meaning and 
importance of his theory. In many of these cases we may suppose that the authors 
had never seen his own original paper, but had obtained their information indirectly 
through the writings of others. 
On the other hand, within the period just mentioned—the first half of the present 
century—real progress was made in many ways, in the gaining of new knowledge and 
the making of a few new discoveries, chiefly in connection with the temporary and 
local disturbances of the atmosphere, and in the bringing together of information of 
various kinds to help in the elucidation of the subject of the winds. The influence of 
moisture in air of any given temperature and pressure in rendering the fluid more 
buoyant was brought effectually into consideration. 
The attainment of information from the practical observations of mariners and 
travellers, and especially explorers of the polar regions, and also from meteorological 
observatories, was making gradual but important progress. Considerable progress was 
made in the collecting and correlating by many persons of observational results as to 
winds and weather and barometric pressures in various latitudes, and in the presenting 
for practical use among navigators and others of the generalized conclusions so derived. 
In that course of progressive labours there were included various speculations or 
theories as to great storms, commonly designated as hurricanes, tornadoes, or cyclones. 
In beginning to touch on this subject I have to mention that from among the many 
persons who may have taken part in researches and speculations regarding cyclones, 
those whom I deem the most noteworthy are Capper, Dove, Redfield, Thom, Eeid, 
and Piddington. 
Now, within the period which we have at present under consideration—the first half 
of the present century—by a very gradual course of experience, chiefly maritime, and 
of speculation based on such experience, it came to be promulgated that violent storms 
were generally great whirlwinds; and so the old name tornado, of Portuguese origin, 
suggestive of turning, and the new name cyclone, used in the sense not merely of 
circular form, but also of revolving motion, came to be accepted as well suited for the 
designation. 
MDCCCXCTI.—A. 4 Q 
