252 HISTORY OF PHYSICAL ASTRONOMY. 



ciable circumstances. In many of the measure- 

 ments of degrees, indications of the attraction of 

 mountains had been perceived ; but at the sugges- 

 tion of Maskelyne, the experiment was carefully 

 made, in 1774, upon the mountain Schehallien, in 

 Scotland, the mountain being mineralogically sur- 

 veyed by Playfair. The result obtained was, that 

 the attraction of the mountain drew the plumb-line 

 about six seconds from the vertical ; and it was 

 deduced from this, by Button's calculations, that 

 the density of the earth was about once and four- 

 fifths that of Schehallien, or four and a half times 

 that of water. 



Cavendish, who had suggested many of the arti- 

 fices in this calculation, himself made the experi- 

 ment in the other form, by using leaden balls, about 

 nine inches diameter. This observation was con- 

 ducted with an extreme degree of ingenuity and 

 delicacy, which could alone make it valuable ; and 

 the result agreed very nearly with that of the Sche- 

 hallien experiment, giving for the density of the 

 earth about five and one-third times that of water. 

 Nearly the same result was obtained by Carlini, in 

 1824, from observations of the pendulum, made at 

 a point of the Alps (the Hospice, on Mount Cenis) 

 at a considerable elevation above the average sur- 

 face of the earth (R). 



