OUTLINES OF NATURAL PHILOSOPHY. 



305. Hence, as the ellipticity of the Earth has 

 been shewn to be less than Q' O^ 2 - T near- 



ly), it is evident, that if the Earth is a spheroid 

 of equilibrium, it is denser toward the interior. 



The greater density of the Earth toward the centre, 

 is in itself probable, and has been put beyond all 

 doubt by very accurate experiments, made on the 

 sides of the mountain Schehallien in Perthshire, 

 by the late Dr MASKELYNE. 



By observations of the zenith distances of stars, 

 the difference of the latitude of two stations on 

 the south and north sides of that mountain, 

 was determined. A trigonometrical survey of the 

 mountain also ascertained the distance between the 

 same two points, and thence, from the known 

 length of a degree of the meridian, under that pa- 

 rallel, the difference of the latitude of the stations 

 was inferred, and was found less by 11 ".6 than 

 by the astronomical observations. 



The zeniths of the stations had therefore been sepa- 

 rated from one another more than in the usual pro- 

 portion of the meridian distance ; and this could 

 only arise from the plummet on each side being 

 attracted toward the body of the mountain. 



From 



