136 OKI GIN OF THE EAETII. 



or the rationally more obvious, portion of the body, still re- 

 tains, in all probability, the general shape and size of the 

 original nebula. If we suppose this spheroid of imponderable 

 matter to be rotating on its own proper axis once in twenty- 

 seven days, seven hours, and forty-three minutes, carrying the 

 earth and moon with it as its condensed foci, we have, in such 

 supposition, an explanation of the motion of the moon round 

 the earth as it appears to us, and of the motion of the earth 

 around the moon as it would be mathematically evident to an 

 inhabitant of the latter body. If this supposition is correct, 

 then neither body ought to move round the other as an abso- 

 lutely fixed point in the system, but both ought to revolve 

 around a common center the axis of their common ethereal 

 and enveloping mass. But, considering the superior attractive 

 force of the earth over the moon, together with the superior 

 density of that whole end of the ethereal mass in which the 

 earth is situated, to that of the end in which the moon is 

 situated, this center of common revolution can probably vary 

 at most but a few hundred miles from the center of the earth, 

 and may be very nearly coincident with it. 



I believe that astronomers are now pretty generally con- 

 vinced that in binary stellar systems, one body not only 

 revolves around the other, but that the two bodies revolve 

 round a common center, situated somewhere between the 

 centers of the two, and nearest to the center of the larger one ; 

 and to these motions, those of the binary system of the earth 

 and moon would, according to the foregoing hypothesis, pre- 

 sent an exact analogy. 



The earth, being the major or positive focal condensation of 

 the general ethereal and enveloping spheroid, has asumed 

 sufficient independence to admit of a diurnal revolution on its 

 own proper axes ; but the moon, being the minor and nega- 



