74 NOTICES OF THE MEBTINGS. [May 9, 1851. 
the velocity of rotation of that point of the earth, were to be sud- 
denly separated by releasing a spring placed between them, and at 
first confined by a string, they would then show the difference of 
velocity, belonging to points on the earth at that distance apart, and 
would consequently revolve round the vertical. (See Comptes Ren- 
dus, 1851, No. 14.) . 
A beautiful variation of the experiment has been suggested by Mr. 
~ Bravais (Comptes Rendus, 1851, No. 6.) in which a perfectly circular 
motion is communicated to a pendulum (by a peculiarly ingenious 
contrivance) the time of whose revolution will be different according 
as its direction conspires with or opposes that of the earth. 
If all torsion in the thread could be got rid of, a ball simply sus- 
pended and furnished with an index in its equator would be seen to 
rotate. But the torsion destroys the effect. This is the suggestion 
of M. Baudrimont (Comptes Rendus, 1851, No. 8.) 
But by far the most complete idea not only of the general prin- 
ciple, but of the precise law of the sine of the latitude, is obtained 
from the beautiful apparatus constructed by Mr. Wheatstone, in 
which the pendulum is replaced by the vibrations of a coiled spring, 
the axis of which can be placed in any required inclination or /atitude 
with respect to a vertical semicircular frame, which is made to revolve 
about its vertical radius, and the direction of the vibrations is seen to 
change in a degree proportioned to the sine of the latitude or ineli- 
ation; as for example for lat. 830 the sine = }: and consequently if 
the vibration be originally in the meridian, when the meridian has re- 
volved 180°, the deviation = 180° x + = 90° or is at right angles 
to the meridian. 
This apparatus was exhibited at the lecture. 
Upon the whole the experiment is one of high interest and import- 
ance: some discrepancies or difficulties in the different views taken of 
the theory as well as in the observed results, seem to indicate that the 
subject, however apparently simple, has not yet been thoroughly 
worked out, — and to point tothe desirableness of further repetitions 
of the experiments, if possible iz vacuo, and with increased precautions, 
as well as to a revision of the dynamical and analytical processes, by 
which possibly any seeming difficulties may be cleared up. 
Bek: 
In the Library were exhibited :— 
Silver chased Sword-hilt, dated 1642, containing ten Portraits, 
Frederick Wilham, Stadtholder of Holland, and his Court. 
The Mouse-deer and the Guanna, mounted by Messrs. Leadbeater. 
Two inlaid Derbyshire Tazzas, &c. [by Mr. Tennant]. 
Lithographed Fac-Similes [by Messrs. Ashbee and Tuckett]. 
Figures in Coloured Biscuit, soft-metal bronzed, and Serpentine 
stone [by Messrs Cundall and Addey]. 
Silver-gilt Shield—‘ Boadicea ” [by Messrs. Hunt and Roskell]. 
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