452 
WILLIAM FERREL. 
in this country. Having arrived at the unexpected conclu¬ 
sion that by overweighting the arm of his gyroscope he 
could cause the revolving disc to rise instead of fall, he had 
an apparatus constructed and experimentally proved the 
truth of his reasonings. 
(8.) 1856.—The germs of Ferrel’s numerous works on the 
winds of the atmosphere and on the currents of the ocean 
as distinguished from the tides are to be found in his pop¬ 
ular and mathematical papers published between 1856 and 
1861. The first of the new ideas which he infused into our 
notions of the mechanics of the atmosphere and the ocean 
consisted in the principle that any object moving horizon¬ 
tally on the earth’s surface under the influence of its own 
inertia and weight and the centrifugal force due to the 
earth’s rotation experiences a deflection to the right in the 
northern hemisphere. This deflection was rightly under¬ 
stood by Poisson and by Tracy, both of whom w T ere un¬ 
known to Ferrel, and he was the first to recognize the 
great value of the influence of the earth’s rotation as 
distinguished from the imperfect consideration of this 
subject that had been promulgated ever since the days 
of Hadley. Ferrel, in fact, showed that in all phenomena 
on a large scale this centrifugal deflection was the item of 
next importance to the density and weight of the air. The 
diurnal rotation also affects the vertical motions of bodies; 
but this he developed in later years. In these early publi¬ 
cations he also considered the influence of the frictional re¬ 
sistance of the earth’s surface to the movement of the air, 
which is next in importance to the effect of temperature and 
of rotation. Having shown the motions that must exist in 
the atmosphere and in the ocean, as produced by gravity 
and density and modified by rotation and friction, he then 
deduced the resulting barometric pressures (or surfaces of 
equal pressure) and completely explained the origin of the 
low barometer in the equatorial and in the polar regions, as 
also in the center of very extended systems of circulating 
winds, and the cause of the belts of high barometer under the 
