THE 
PHILOSOPHICAL MAGAZINE 
AND JOURNAL. 
SEM ARCH : 1896; 
XXIV. On the Figure of the Earth. By Wuu1am Gat- 
BRAITH, Esq. M.A. 
To the Editor of the Philosophical Magazine and Journal. 
Sir, 
[NX some of the previous Numbers of your Journal I was in- 
duced to make a few remarks on several of the most ac- 
curate systems of experiments by the pendulums hitherto exe- 
cuted for the purpose of determining the figure of the earth. 
Since that time Captain Sabine’s work on that subject has ap- 
peared, containing an extensive series of experiments in the 
northern hemisphere, reaching from the equator to about 30° 
north latitude, embracing the longest arc of the meridian yet 
attempted ; and executed, it is believed, with an accuracy which 
cannot easily be surpassed. Capt. Sabine has also reconsidered 
some of the experiments of others, particularly those made b 
the French mathematicians on the arc passing chiefly through 
France ; and, by applying corrections analogous to those em- 
ployed by himself, has by that means rendered them more 
consistent, and comparable with each other, and with his own. 
By the French experiments it appeared from the character of 
the errors,—Phil. Mag. vol. Ixiv. p. 167, but more especially 
from vol. Ixy. p. 15,—that the gravitating force at about 45° N, 
was less from experiment than theory required, so far as the 
accuracy of these experinients could be depended upon; or in 
other words, that the pendulum was more distant from the 
centre of the earth than could have been anticipated : and this 
conclusion seemed to derive some support from the compres- 
sion obtained from the measurement of arcs near the mean 
parallel. 
Whether this conclusion, which it must be admitted is not 
very natural, is to be ranked among those views which the 
early French mathematicians entertained, in opposition to 
Newton, remains to be determined. Perhaps the nature of the 
ground over which the are passed, when properly examined, 
Vol. 67. No. 335. March 1826. would 
