1865.] The Proposed Pendulum Operations for India. 265 
pendulum. He concluded from all his results, that even if a pendulum 
is formed of materials having the same specific gravity, yet if it be 
not of an uniform shape throughout, each distinct portion must be 
-made the subject of a separate computation, in order to determine the 
correct vibrating specific gravity of the whole body, since each part 
will be differently affected by the surrounding air. 
The last extensive series of experiments were those taken in 
1828-31 by Captain Henry Foster, who was sent out on a scientific 
mission by the Board of Admiralty. He took out with him four 
invariable pendulums of different metals, two of Captain Kater’s 
pattern, and two of Baily’s convertible pattern. These last consisted 
of a plain straight bar, 2 inches wide, $ inch thick, and 5 feet 24 
inches long, having two knife edges 39.4 inches apart, but no heavy 
bob or sliding weights, as in Captain Kater’s pattern ; the synchronism 
was adjusted by filing away at one end of the bar. Baily’s intention 
was, that the pendulum should either be used as two different invari- 
able pendulums, or applied as a single convertible one for absolute 
determinations at any station. The objection to the form is, that both 
the knife edges must be exactly perpendicular to the bar, or error is 
entailed, as the bar is not flexible like Kater’s. Captain Foster 
swung pendulums at all his stations, 14 in number, which were chiefly 
in the southern hemisphere. He made a set of observations at Mr. 
Browne’s house before the voyage; on the return of the pendulums 
to England, they were again swung at the same place, but by Mr. 
Baily, Captain Foster having been most unfortunately drowned in the 
River Chagres, in February 1831, just as his mission was completed. 
His observations were reduced by Mr. Baily, who obtained from them 














an ellipticity of 515.5. 
About this time the Russian government sent out an expedition 
under Captain Liitke, who used an invariable pendulum, formerly used 
by Captain Basil Hall. He swung it first at Greenwich, and after- 
wards at Ualan, in the Caroline islands, Guam, Bonin island (to the 
“usual manner. Then will the required vibrating specific gravity of the pen- 
* dulum be aie 
aw’ a’ + w" dt + w” gq’ ate an, 
= 1 a’ we a” we a! ‘ 
p+ tt 
Sal 



s 
(Philosophicab Transactions, 1832.) 
