PHYSICAL ASTRONOMY. 307 



Earth, and to the planets which are known to re- 

 volve on their axes. 



The distribution of the solid materials in the interior 

 of the Earth, will very much affect the nature of 

 this solid, and the manner in which the figure is 

 acquired must probably prevent the approxima- 

 tion from ever being complete. 



The distribution of the materials at any distance un- 

 der the surface is unknown, and we have no means 

 of examining into it, but by the measurement of 

 degrees, or by experiments on the pendulum, and 

 on the plumb-line, like those at Schehallien. 



310. On the whole, the facts known, from ob- 

 servation, about the figure of the Earth, agree 

 in general with theory ; but there are in the 

 expressions of that theory, so many quantities 

 which are yet indeterminate, that the perfect 

 coincidence of the two cannot be affirmed. 



SECT. 



