268 Notices of Bookj;. [April, 



of late been often and accurately estimated. As to the heat, it 

 has been calculated that if the sun's heat were distributed 

 uniformly over the surface of the earth it would in one year 

 suffice to liquefy a layer of ice ioo feet thick ; and this amount 



of heat, be it remembered, is only the - — B — th part of the 



' j 2,130,000,000 r 



heat emitted by the sun in the course of one year. The absolute 



Fig 



The same group as shown on the last page ten minutes later. 



luminosity of the sun's surface is more than 146 times the 

 luminosity of the lime light. The subject of the dissipation of 

 energy and the maintenance of the sun's heat finds ample dis- 

 cussion in this chapter. 



The last chapter is entitled " The Sun among his Peers." 

 The sun, as is well known, possesses proper motion of his own; 

 he is ca rried forward in space, and with him all the members 

 of the solar system which revolve around him. We do not 

 know, however, whether any of his brother suns accompany 

 him. As the earth is carried along with the sun, while it rotates 

 around him, the path followed by it is a helicoidal path. 



" Jupiter is carried some 1,700,000,000 miles onward with the 

 advancing sun, while he circuits once around his orbit of less 

 than 1,000,000,000 miles in diameter; Saturn sweeps on through 

 some 4,400,000,000 miles while circuiting his orbit, less than 

 1,850,000,000 miles in diameter; and the paths traversed by 

 Uranus and Neptune amid the depths of sidereal space are even 



