Hull — On the Effect of Continental Land on Level of Ocean. 651 



creasing distance of bodies on the earth's surface from the centre of 

 the earth, due to the oblate-spheroidal form of the earth itself ; and, 

 secondly, on account of the decrease of gravity due to the increas- 

 ing centrifugal force depending on the velocity of the earth's rota- 

 tion. Both these causes act in the same direction in lessening the 

 gravity of bodies towards the equator ; and, as a consequence, 

 causing a decrease in the length of the second's pendulum. The 

 total variation in the length between those at the equator and 

 the poles amounts to 0*222 of an inch. 1 



■From the data thus obtained we can determine the number of 

 oscillations of a pendulum of the same length (or the same pendu- 

 lum) on a continental and oceanic station ; and, applying the for- 

 mula stated by Suess, viz. 122 times the difference in the number 

 of oscillations at two stations on (nearly) the same latitude, we 

 obtain the result in metres. 



The results of the Grerman physicists will probably surprise 

 many who have been under the impression that the difference 

 of level of the surface of the ocean, relatively to a geodetic 

 surface, does not very much vary. Comparing the maximum 

 and minimum results, it will be observed that the difference 

 of level between California (or Mexico) and the Sandwich Islands 

 amounts to no less than 4520 feet. The great rise in the ocean 

 surface along the coast of California is accounted for by the extent 

 and elevation of the mountain ranges along the American coast ; 

 and this notwithstanding the existence of the Grulf between the 

 peninsula and the main land. The attractive influence of a moun- 

 tain range near the coast is here clearly illustrated ; and even more 

 remarkable results might be expected, were a comparison instituted 

 between stations on the coast of Peru and the Marquesas, or Society 

 Islands, in the centre of the Pacific. 2 



Having called the attention of the President of the Royal 

 Society, Professor Gr. Gr. Stokes, to the statement in Suess's work, 

 in which his name appears, and requesting his views thereon, I 

 have been favoured with the following reply, which is inserted by 

 permission : — 



1 Haughton, " Natural Philosophy." 



2 It is greatly to be desired that pendulum observations should be undertaken on 

 the Peruvian coast. The Sandwich Islands would then answer for comparison. 



