Captain Hall’s and Mr Henry Foster’s Experiments, <^c. 91 
spect, as well as in its mode of life, it is also distinct from S. sylva- 
ticus, to which, in other particulars, it has a considerable affinity. 
Two very perfect specimens of Carahiis catenatus fell into our 
hands alive. Of less value were Rhagium mordax and Lamia 
curciilionoides, which we saw upon young bi;anches of shrubs, 
and Carabus convexus, which we found under stones. 
{To he continued.) 
Art. XII. — Account of Captain Basil Hall’s and Mr Henry 
Foster’s Experiments with an Invariable Pendulum, made 
near the Equator, and on the Coasts of Mexico, and Brazil 
HEN Captain Hall left England in 1820, in his Majesty’s 
ship Conway, for the South American station, an invariable pen- 
dulum was, at Captain Kater’s suggestion, put into his hands by 
the Board of Longitude. As the service, however, upon which 
this officer was sent, was unconnected with scientific objects, it 
was only at particular intervals of active professional employment, 
that he could command the requisite leisure for philosophical in- 
quiries. Through the indulgence, it appears, of Sir Thomas 
Hardy, Bart, K. C. B., the commander-in-chief, he was enabled to 
make three sets of observations with the pendulum, viz. at- the 
Galapagos, a group of islands in the Pacific Ocean ; at San Bias 
de California, in Mexico ; and at Bio de Janeiro in Brazil. 
The Galapagos Islands being under the Equator, Captain 
Hall was desirous of making his observations exactly under that 
great circle ; but, from the ship being swept to leeward in the 
course of the night, and from the small number of days which 
he was allowed to spend at this place, he was forced to take a 
station at the south end of Abingdon Island, formed of lava, and 
about 32 1 miles north of the Equator. 
The longitude of the station was 90|° W., and its latitude 
0° 32' 19" N. ; and the number of vibrations made by the pendu- 
lum, in a mean solar day, was 86101,34, at the level of the sea, 
in vacuo, at 68° of Fahrenheit. As the same pendulum in Lon- 
* These experiments are published in detail in Philosophical Transactions 
for 1823, Part II, p. 211— 289. 
