DEVELOPMENT OF METEOROLOGY—ABBE. 299 
difficult branches of mathematics and analytic mechanics, and these 
subjects have not yet been developed to an extent sufficient to handle 
any but the simplest of the problems of nature. 
As we read the scientific literature of the eighteenth century we 
find Euler, in his “* Mechanics” (1736), developing the fundamental 
formule for the movements of dry gases and ideal liquids, after he had 
proceeded as far as he could with the mechanics of rigid bodies. In 
his prize essay of 1746 D’Alembert developed a theory of the winds. 
We pass then to the great French mathematicians, Lagrange, Poisson, 
and Laplace, and the English mathematicians, Green and Stokes, to 
all of whom we owe investigations of the laws of motions of fluids 
under two essentially different conditions, namely, when a velocity 
potential exists and when it does not exist. In 1851-1855 appeared 
the memoir of Stokes on viscosity and in 1857 the famous memoir of 
Helmholtz on vortex motions, each of which removed difficulties 
that had hitherto obstructed our progress. The works of Sir Wil- 
ham Thomson, now Lord Kelvin, on thermodynamics and on cireu- 
latory motion, and the persistent researches of Bjerknes, father and 
son, in the application of vector analysis, have clarified our ideas 
and represent our present highest attainments in this branch of 
mechanics. Just as meteorologists have hitherto been dependent 
upon physicists for the apparatus with which to observe, and upon 
the mathematical physicists for the explanation of the optical and 
thermal, the acoustic and the electric phenomena of the atmosphere, 
so now they are coming to be more and more dependent upon the 
higher mathematicians to resolve the analytical difficulties inherent in 
the complex problems of fluid motion. 
It is very rarely that the meteorologist arrives at a phenomenon 
deductively and then examines the records of observation to see if it 
actually exists. Ferrel did this in a few cases; but usually we have 
proceeded by slow inductive methods. For instance, the Phcenician 
voyagers and the Greeks who penetrated into India knew of the 
existence of the southwest monsoon, but a complete knowledge of its 
origin and nature has required centuries of observation and the labors 
of men of great talent in mechanics. Fifty years ago it was assumed 
in a general way that the heated air over the interior of Asia, by 
expanding and overflowing, gave rise to an indraft corresponding to 
the sonthwest monsoon; but it remained for Ferrel, about 1880, to 
show that it was not merely a heated interior, but a heated high 
plateau that was necessary to produce this great current; and it was 
not until 1890 that Sir John Eliot showed that this monsoon current 
is by no means a simple disturbance of the northeast trade winds that 
are appropriate to the latitudes of India, but that we have to go much 
farther south, far across the equator, and see that the whole southeast 
trade-wind system of the southern Indian Ocean is perverted from 
