174 ASTRONOMICAL HISTORY. 



seems to furnish the cause of almost none of its changes. 

 If it is conceded, (which indeed is not improbable), that 

 the earth itself too, and not heavenly bodies only, acts 

 upon the fields of air, either by an efflux of cold, or by 

 emitting winds, or some other similar modes, still all that 

 variety is ascribed only to some portions of the earth in 

 immediate contact with the air itself, in which none will 

 deny there exists a multitude of changes and vicissitudes. 

 But it must be fully admitted that, of the phenomena of 

 the earth, earthquake enters the deepest by far into its 

 bowels ; and, which are of the same class, gushes of 

 water, volcanoes, fissures and convulsions of the earth and 

 the like, which notwithstanding do not seem to rise from a 

 great depth, since most of them generally affect but a cer 

 tain limited portion of the earth s surface. In proportion 

 as an earthquake affects a larger space on the earth s sur 

 face, in the same proportion we are to infer that its roots 

 and source enter deep into the mass of the earth ; and the 

 contrary, in proportion as it is less extensive. But if any 

 one should allege that there sometimes happen earthquakes 

 which shake large and extensive tracks of country, no 

 doubt it is so. Yet these rarely occur, and are among the 

 number of the greater calamities of the species, and may 

 therefore be compared to the higher order of comets, which 

 are also of rare occurrence. For we do not now discuss 

 whether eternity absolutely may be affirmed of the earth, 

 but would make it appear, as we stated at the commence 

 ment, that with reference to constancy and mutation there 

 is no great difference between heaven and earth. We do 

 not consider it worth while to contend for the eternity of 

 the earth from the modes of its motion. For it were 

 superfluous to argue eternity from the properties of motion, 

 since, if a circular motion is without a limit, so is rest : eter 

 nity may equally be predicable of the coherency of com 

 pact and large masses of homogeneous substance, as of the 

 rotation of rarer bodies; the parts detached from either 

 flying off in right lines. 



This also may be assumed in reasoning upon the point, 

 that the internal parts of the earth are not more exposed 

 to decay than heaven itself; because something generally 

 perishes of that body wherein something can be repaired. 

 Now when showers, and substances which are precipitated 

 from the air, and which renew the upper surface of the 

 earth, in no way find a passage into the interior parts of 

 the earth, which nevertheless remain fixed by their own 



