219 
made with an invariable pendulum. 
and especially at the Falkland Islands (which lie in the cor- 
respondent latitude to that of London), and at various other 
stations on the main land, or on large islands, is still more 
9 
obvious. 
At page 240 you will observe the details of the ellipti- 
cities deduced ; and it is sufficient to mention here, that 
the length of the second's pendulum at the Galapagos is 
39.01717 inches, and the mean of all the ellipticities thereby 
deduced from your experiments in England, — ^ and from 
those of Captain Sabine at Melville Island, — — 
1 292.14 
SAN BLAS DE CALIFORNIA.* 
The tables No. III. contain the details of the experiments 
made at San Bias, a sea port town on N.W. coast of Mexico, 
in latitude 2i£° N. and longitude 105^° W. and not far from 
the south point of California. These experiments were per- 
formed under favourable circumstances, the sky being clear, 
the temperature steady, and the rate of the clock uniform. 
The station indeed was more elevated than could have been 
wished, being 115 feet above the level of the sea, on the 
summit of a cylindrical rock of compact whin stone, and 
measuring not more than 500 feet across, and nearly perpen- 
dicular in three quarters of its circumference. 
The length of the seconds pendulum at San Bias, by these 
experiments, comes out 39.0377 6 inches, and the mean el- 
lipticity 
313-55 
By a second series of experiments at San Bias, the details of 
which are given by my coadjutor, Mr. Henry Foster, Mas- 
* San Bias is in Mexico, but being near California, it takes that addition to 
distinguish it from other towns of the same name. 
