18 COSMOS. 



the effects of gravity in continental regions may indeed ren- 

 der a gradual change inappreciable to actual observation ; 

 and, according to Bessel's calculation, in order to increase 

 the latitude of a place by a change of only l /x , it must be 

 assumed that there is a transposition in the interior of the 

 earth of a mass whose weight (its density being assumed to 

 be that of the mean density of the earth) is that of 7296 ge- 

 ographical cubic miles. ^ However large the volume of this 

 transposed mass may appear to us when we compare it with 

 the volume of MonJ Blanc, or Chimborazo, or Kintschind- 

 jinga, our surprise at the magnitude of the phenomenon soon 

 diminishes when we remember that our terrestrial spheroid 

 comprises upward of 1696 hundreds of millions of such cubic 

 miles. 



Three different methods have been attempted, although 

 with unequal success, for solving the problem of the figure 

 of the earth, whose connection with the geological question 

 of the earlier liquid condition of the rotating planetary 

 bodies was known at the brilliant epoch of Newton, Huy- 

 gens, and Hooke.j These methods were the geodetico-as- 

 tronomical measurement of a degree, pendulum experiments, 

 and calculations of the inequalities in the latitude and lon- 

 gitude of the moon. In the application of the first method 

 two separate processes are required, namely, measurements 

 of a degree of latitude on the arc of a meridian, and meas- 

 urements of a degree of longitude on different parallels. 



Although seven years have now passed since I brought 

 forward the results of Bessel's important labors in reference 

 to the dimensions of our globe, in my General Delineation 

 of Nature, his work has not yet been supplanted by any one 

 of a more comprehensive character, or based upon more re- 

 cent measurements of a degree. An important addition and 

 great improvements in this department of inquiry may, how- 



* Bessel, Ueber den Einfluss der Veranderungen des Erdkorpers anf 

 die Polhohen, in Lindenau und Bohnenberger, Zeitschrift fur Astrono- 

 mic, bd. v., 1818, s. 29. "The weight of the earth, expressed in 

 German pounds 9933 XlO' 21 , and that of the transposed mass=947 

 X 10- u ." 



f The theoretical labors of that time were followed by those of 

 Maclaurin, Clairaut, and D'Alembert, by Legendre, and by Laplace. 

 To this latter period we may add the theorem advanced by Jacobi, in 

 1834, that ellipsoids of three unequal axes may, under certain condi- 

 tions, represent the figures of equilibrium no less than the two pre- 

 viously-indicated ellipsoids of rotation. See the treatise of this writer, 

 whose early death has proved a severe loss to science, in PoggendorfFs 

 Annalen der Physik und Chemie, bd. xxxiii., 1834, s. 229-233. 



