DECEMBER 1, 1899. ] 
equilibrium, disturbed at the surface by the 
effect of the winds. The conditions are 
nearly identical. In the Baltic, easterly 
winds and currents force the waters into the 
North Sea, raise the level of the Great Belt, 
and give rise to an undercurrent from the 
North Sea into the Baltic. Here we assume 
that the waters, which the equatorial cur- 
rents succeed in piling up in the western 
part of the Caribbean Sea, seek a passage 
through the Yucatan Strait into the Gulf 
of Mexico; that in this passage the level 
stands higher than on either side, and 
that the water forced into the Gulf of 
Mexico raises its level over that of the 
eastern portion of the Caribbean Sea. Since 
equilibrium cannot be restored at the sur- 
face, it is done byan undercurrent from the 
Gulf. Somewhat different from these con- 
ditions are those which are supposed to 
govern the flow of the Gulf Stream from the 
Gulf of Mexico into the Atlantic. Pills- 
bury’s current observations in the Strait of 
Florida show that in the narrow parts the 
current touches bottom. There remains 
little doubt at present that the Gulf Stream 
owes its origin to the difference of level be- 
tween the Gulf of Mexico and the Atlantic. 
Recent precise leveling, by the Coast and 
Geodetic Survey, indicates that between the 
mean level of the ocean at St. Augustine, 
on the eastern coast of Florida, and that of 
the Gulf at Cedar Keys, on the western, 
there exists a difference of nine-tenths of a 
foot. Some surprise might be expressed 
that such an insignificant difference should 
be able to set such a powerful stream into 
motion. But if we assumethe Gulf to rep- 
resent a basin, and the Strait of Florida a 
narrow orifice by which it communicates 
with the Ocean and apply Torricelli’s 
theorem, neglecting friction, we obtain the 
velocity of vx=V29x 0.9=7.6 feet per 
second, which is not very greatly in excess 
of the average velocity of the Gulf Stream 
in the most contracted portion of the Strait. 
SCIENCE. 
807 
Some authors speak of the impulse of 
the Gulf Stream carrying its waters against 
the western coast of Europe, and producing 
a higher level there than exists on the east- 
ern coast of North America. Whatever 
impulse the Gulf Stream possesses is due to 
its higher level, and I cannot comprehend 
how such an impulse can make it ascend an 
inclined plane. What is meant, I presume, 
is the Gulf Stream drift, the motive power 
of which is the prevailing westerly winds 
of the North Atlantic. It is generally sup- 
posed that this Gulf Stream drift is compen- 
sated for by an undercurrent setting from 
the western shores of Europe in a south- 
westerly direction. 
A. LINDENKOHL. 
OBSERVATIONS ON RHYTHMIC ACTION. 
Two entirely different forms of regularly 
repeated action are tobe distinguished. In 
one form the subject is left free to repeat 
the movement at any interval he may 
choose. This includes such activities as 
walking, running, rowing, beating time, 
and soon. A typical experiment is per- 
formed by taking the lever of a Marey tam- 
bour between thumb and index finger and 
moving the arm repeatedly up and down ; 
the recording tambour writes on the drum 
the curve of movement. Another experi- 
ment consists in having the subject tap on 
a telegraph key or on a noiseless key and 
recording the time on the drum by sparks 
or markers. Other experiments may be 
made with an orchestra leader’s baton hay- 
ing a contact at the extreme end, with a 
heel contact on a shoe, with dumb-bells in 
an electric circuit,and soon. For this form 
of action I have been able to devise no 
better name than ‘ free rhythmic action.’ 
In contrast with this there is what may 
be called ‘ regulated rhythmic action.’ This 
is found in such activities as marching in 
time to drum-beats, dancing to music, play- 
ing in time-to a metronome, and so on. A 
