304* OUTLINES OF NATURAL PHILOSOPHY. 



surement of degrees, and from experiments with 

 the pendulum. 



As, in the actual figure of the Earth, the compression, 

 or the ellipticity, is nearly .0032, 60. if we take 

 this from .008695, the remainder, .005495, or 



- , is the diminution of gravity from the pole to 



the equator. And the gravitation at any other 

 . point of the spheroid, is g ( 1 + .005495 sin* A), 

 g being the gravity at the equator. The length of 

 an isocronous pendulum is expressed by the same 

 formula. This agrees nearly with the observa- 

 tions on the length of the pendulum in different 

 latitudes. See a Table of them, VINCE, Astron. 

 vol. n. p. 105. LA LANDE, Astron. $ 2712. BIOT, 

 Astron. torn. ur. p. 14-8.' 



The lengths of the pendulum in different latitudes, 

 are less subject to irregularities than the lengths 

 of degrees ; the intensity of gravity being, as 

 might be expected, less affected by local variations 

 than its direction. 



307. The inequalities on the surface of the 

 Earth, and the unequal distribution of the rocks 

 which compose it, with respect to density, must 

 produce great local irregularities in the direc- 

 tion of the plumb-line, and are probably the 

 causes of the inequalities observed in the mea- 

 surement 



3 



