THE WORK OF THE FORCES WITHIN. Ill 



by the action of the elastic powers within the 

 earth. 



A general view will now convince yon that the 

 phenomena of burning mountains and earthquakes, 

 ami the discharges of gases and steam, as well as 

 hot springs, are but the last remaining tokens of 

 those mighty natural forces, which in the first ages 

 rocked our earth in its cradle, — by which, through a 

 long succession of struggles and revolutions, during 

 periods of time that the measure of history cannot 

 span, its surface was wrought into its present form, 

 — by which the sea was divided from the land, the 

 highlands and mountains raised up, and the valleys 

 brought low, the courses planned for the rivers, 

 and the beds prepared for the lakes. 



But even these last traces of still active under- 

 ground power must by degrees dwindle away. 

 Great quantities of heat, as you have seen, are 

 every year withdrawn from the bowels of the earth 

 by the hot springs, the steam-jets, and the lava- 

 streams ; though all this, it is true, is but a small 

 fraction of the immeasurable stores which still 

 remain behind. But these losses are not repaid ; 

 and all the losses are added together in the course 

 of years. Besides this, it is likely that, by the 

 gradual cooling of the earth, even more is lost than 

 by the means which I have mentioned. And even 

 if the outermost crust of the earth be an exceed- 

 ingly bad conductor, and if it do receive daily from 



