454 
WILLIAM FERREL. 
diameter of a circle. This series particularly interested the 
late Prof. Benjamin Peirce, through whom it was presented 
to the National Academy of Sciences in 1865. 
(11.) 1865.—As the result of a discussion of the tidal 
observations made at Brest, Dausy had concluded that a 
very small disturbance of the tides is produced by violent 
winds from the north or northeast and from the south. 
From this result Ferrel showed that the average effect of 
all the winds for the months or the year must be inappre¬ 
ciable at Brest. After correcting the observed monthly 
mean heights for local barometric pressure and for terms in 
the tidal formulae depending upon the sun’s declination and 
for the local wind effects, as found by Dausy, Ferrel demon¬ 
strates the existence both at Brest and at Key West of an 
appreciable annual fluctuation in the monthly means of the 
height of the sea. These stations on opposite sides of the 
Atlantic ocean feel the influence of a rise and fall in the sur¬ 
face of the sea caused by its general gyration about a central 
region. This gyration had been deduced as probable in 
Ferrel’s memoir of 1861, and the present investigation estab¬ 
lished its actual existence and numerical value. The most 
rapid gyratory motion takes place in April, when the water 
is highest in the center of the ocean and lowest at Brest and 
Key West. The slowest gyration occurs in October or No¬ 
vember, when the water stands a little lower in the center 
and higher at Brest and Key West. 
(12.) 1873.—Having demonstrated the existence of an an¬ 
nual and possibly also a lunar monthly period in the velocity 
of the Gulf Stream (very much such as would now appear to 
result from the observations just published by Lieutenant 
Commander Pillsbury in the Annual Report of the Coast 
Survey for 1890), Ferrel, in 1873, published a further dis¬ 
cussion of meteorological effects upon the heights of the 
tides with a special reference to the Boston harbor observa¬ 
tions. He shows that an average northeast wind raises the 
sea-level only about three inches, and a southwest wind de¬ 
presses it not quite so much. The very strongest winds 
