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XVII. Bakerian Lecture.— On the Grand Currents of Atmospheric Circulation. 
By James Thomson, LL.D., F.R.S., Emeritus Professor of Civil Engineering and 
Mechanics in the University of Glasgow. 
Received March 10,—Read March 10, 1892. 
[Professor Thomson died on May 8, 1892, before this Lecture was printed.] 
In the early times of the Royal Society (a little more than 200 years ago) a spirit of 
inquiry and of speculation as to the causes of the Trade Winds arose among its 
members. The papers which we may presume to have first brought the subject into 
special notice in the Society, and which were published in the ‘ Transactions,’ offered 
view r s which, in the light of subsequent knowledge and theory, show themselves as 
being untenable, and in part even grotesque. But those papers were soon followed 
by, and probably had an effect in leading to, a much more important paper by the 
eminent astronomer Edmund Halley ; and this was followed 49 years later by one, 
more important still, by George Hadley, in which we may with confidence judge 
that a substantially true theory of a large part of the system of Atmospheric 
Circulation in its grandest and most dominant conditions was for the first time 
offered to the world through the pages of the ‘ Philosophical Transactions.’ 
Further speculations on the subject and advances in our knowledge of it have been 
made in later times and have been brought into notice in various ways. I believe 
that I have myself arrived at some improved considerations which are to a large 
extent trustworthy and go far towards completing the true theory of the grand 
currents of atmospheric circulation, and I entertain the ambition to have my views 
placed on record by this Society—the Society in which the subject had its most 
important beginnings. 
With this in view it appears indispensable that some historical recital should be 
adduced of the progress made by others previously: but still, for those who may 
at any time wish to direct their attention specially to the physical conditions 
irrespective of the history of the progress of thought or of discovery on the subject, 
it appears desirable that an exposition of the resultant theory which I have devised 
should be presented without being itself encumbered by historical details of the 
courses through which it has been ultimately arrived at. I propose, therefore, to 
present, in a first section, a historical sketch of all the speculations and theories 
which, as far as known to me, have conduced in any important way towards the 
resulting theory that I have to offer as being tenable and trustworthy ; and then to 
set forth that new theory itself divested as far as possible of historical or personal 
19 12.92 
