310 NOTES TO BOOK VII. 



Longitude depending upon the distance of the Moon's 

 Node from the Equinox. Doubts were entertained by 

 astronomers whether this inequality really ^existed ; but 

 Laplace showed that such an inequality would arise from 

 the oblate form of the earth; and that its magnitude 

 might serve to determine the amount of the oblateness. 

 Laplace showed, at the same time, that along with this 

 Inequality in Longitude there must be an Inequality in 

 Latitude ; and this assertion, Burg confirmed by the dis- 

 cussion of observations. The two Inequalities, as shewn 

 in the observations, agree in assigning to the earth's form 

 an Ellipticity of l-305th. 



(R.) p. 252. " Cavendish's Experiment" to deter- 

 mine the density of the earth has been repeated recently 

 by Prof. Reich at Freiberg, and by Mr. Baily in England, 

 with great attention to the means of attaining accuracy. 

 Prof. Reich's result for the density of the earth is 5,44. 

 Mr. Baily's is 5,92. Cavendish's result was 5,48 ; ac- 

 cording to Button's revision of the calculations it became 

 5,32 ; but this revision is inaccurate, as Mr. Baily has 

 shown. On being again revised by Edward Schmidt, the 

 result is 5,52. I quote this latter result from M. de 

 Humboldt, Kosmos, p. 424. 



(s.) p. 259. That there would be, in the tidal move- 

 ments of the ocean, inequalities of the heights and times 

 of high and low water, corresponding to those which the 

 equilibrium theory gives, could be considered only as a 

 conjecture, till the comparison with observation was made. 

 It was, however, a natural conjecture ; since the waters of 

 the ocean are at every moment tending to acquire the 

 form assumed in the equilibrium theory : and it may be 

 considered likely that the causes which prevent their 



