OBITUARY NOTICES. 
457 
tardation of the earth’s rotation and its application to the 
secular acceleration of the moon’s motion. He shows that 
the earth must have an effect on the moon 6,000 times that 
of the moon upon the earth, and must therefore have long 
since forced the lunar rotation to coincide with its revolu¬ 
tion about the earth. 
(14.) 1874.—The closing paragraph of the “ Tidal Re¬ 
searches ” connects his paper of 1854 on the “ Internal Flu¬ 
idity of the Earth ” with the present study of tides, and sug¬ 
gests that we have now succeeded for the first time in 
demonstrating a real cause as to why the exterior and inte¬ 
rior of the earth should have different periods of rotation, 
and have thus taken one step toward rendering possible the 
truth of Halley’s hypothesis of concentric magnetic shells 
and an internal nucleus to account for secular changes in 
the earth’s magnetism. 
(15.) 1871-1883.—Ferrel closed his work on tides for the 
Coast Survey by the invention and successful construction 
of a machine for predicting the maxima and minima of the 
tides. This machine is said to do the w T ork of 30 or 40 com¬ 
puters and has been regularly used since 1884. 
(16.) In meteorology Ferrel accomplished so great a work 
that it is impossible here to properly condense it, but I may 
enumerate a few more prominent items. His law connect¬ 
ing the velocity and direction of the wind with the baro¬ 
metric gradient was presented first to this Philosophical 
Society in 1874. It expresses the total effect of the two im¬ 
portant considerations, namely, the rotation of the winds 
around a storm center plus the rotation around the earth’s 
axis, and enables us at any time to compute the separate 
effects of the local and the general circulation of the atmos¬ 
phere. 
(17.) 1877-1881.—The general principles that control the 
development and progressive motions of storms were ex¬ 
plained by Ferrel in his “ Meteorological Researches,” part I, 
and the detailed thermo-dynamic phenomena of storms were 
given in full in his “ Meteorological Researches,” part II. 
60—Bull. Phil. Soc., Wash., Vol. 12. 
