INORGANIC EVOLUTION 31 



which has wrought the solar system into form has not 

 yet finished its work ; it is still in progress. The work 

 is very nearly done; and when that work shall have 

 been completed the satellites of Uranus and Neptune 

 will no longer be dissociated from the general concord." 

 (Ball). 



Arrhenius thinks that the outer portions of the 

 primeval nebula were so attenuated, that the immigrat- 

 ing bodies which formed the nuclei for Uranus and 

 Neptune, did not attain sufficient volume to have the 

 large common rotation, in the equatorial plane of the 

 sun, impressed upon them by the tidal effects. For 

 this reason, their moons are independent of the general 

 concordance of movement in common plane. 



RADIUM. The discovery of radium is likely to change 

 the ideas now in vogue regarding the age of the earth, 

 and is most important to its geology. Heretofore it was 

 thought there was nothing to replace the apparent 

 loss of heat which flows from the interior to the sur- 

 face. If there is nothing within the earth to replace 

 this heat, then, according to the calculations of Lord 

 Kelvin, the earth is only about a hundred million 

 years old. But since a small particle of radium has 

 been derived from the earth by Madam Curie, new 

 estimates have greatly extended this time. Professors 

 Strutt and Joly have determined that there are in the 

 earth only five grammes of radium to a cube, whose 

 side is one hundred miles ; yet the heat given out by 

 this small particle is so great that it is more than 

 enough to replace the lost heat. It is calculated 

 that if there were as much radium throughout the 

 interior as in the crust, the heat would increase much 

 more rapidly than it does from the surface toward the 

 center. According to this theory, the rocks of the 



