LIFE ON THE EARTH. 161 



and many repetitions in the economy of nature to 

 produce a sensible effect 1 . 



Passing without remark conjectures regarding the 

 limits of the precession of the equinoxes, and the ob- 

 liquity of the ecliptic, and estimates of the variation 

 of the diameter of the earth's orbit, by which it has 

 been attempted to meet the difficulties of ancient 

 geological climate, a few words may be added re- 

 garding one speculation which has justly received 

 more serious consideration. The interior tempera- 

 ture of the earth is observed to augment sensibly 

 as we descend; the figure of the earth indicates ori- 

 ginal fluidity; the lowest rocks agree with the opi- 

 nion that great heat has been an essential agent in 

 giving to them their present appearance. The earth 

 is hotter within than at the surface; receives a cur- 

 rent of heat from the interior, and dissipates it into 

 space; grows cooler, and has been always growing 

 cooler, from the earliest times. Why not suppose 

 the greater surface-heat of early times to have been 

 caused by the then greater and nearer influence of 

 the interior much heated masses? The influence of 

 such a flow of heat outward to all parts of the sur- 

 face, independent of latitude, is exactly of such a kind 



1 Col. Sir H. James has attributed a great effect to this cause, 

 AthencBum, Sept. 1860. Remarks have followed by Professor 

 Airy, Professor Jukes, and Professor Hennessy, which agree 

 with the views expressed in this work. 



K. L. M 



