2t A Period in the History of our Planet. 



life, if I may so express myself, came in place of the torpid inac- 

 tivity of the frozen masses. Clefts opened under the expansive 

 force of the solar heat, and thus furnished the waters which 

 the melting of the superficial strata called forth in copious 

 abundance with a welcome outlet below, where, in the rolled 

 materials of the soil, they dug themselves beds, bounded and 

 protected by the crystal walls which they had just broken 

 through. 



Although at present, in the attenuated atmosphere of our lofty 

 mountains, the evaporation of the frozen masses of ice and 

 snow, especially in warm days, far exceeds what melts into 

 fluid water, the proportion must have been very different on 

 those extensive plains which, less elevated above the level of 

 the sea, stood under a much more considerable pressure of the 

 atmosphere. Moreover, the very slight inclination, or rather 

 the almost perfect levelness of these plains, was not very fa- 

 vourable to the formation of frequent clefts and fissures, so 

 that the glacier brooks composed of the different rills on the 

 surface of the ice, must have been much more considerable 

 than those of our present glaciers, where for the most part a 

 comparatively limited surface, frequent fissures, and smaller 

 pressure of the atmosphere, prevent the accumulation of larger 

 brooks upon the surface of the glaciers. There are but few 

 brooks to be found upon the surface of our Alpine glaciers, 

 over which the practised leaper would hesitate to spring. But 

 at the period I am now discussing, the crystal floods of large 

 rivers dug their mutable beds out of the extensive surface, 

 and when at length, after a long course, a fissure afforded 

 them the long-sought outlet, they threw themselves in mag- 

 nificent falls into the azure depths, the immense strata of 

 rolled matter and of sand which the icy mass by its grinding 

 movement collected below it, grubbing through to the bottom. 

 Circumscribed by the ice-walls, these glacier rivers gnawed 

 vaults for themselves under the icy covering through which 

 they pressed towards the greater depths which the uneven sur- 

 face presented, undermined deep beds in the rolled matters, and 

 thus produced valleys of denudation, the direction of which is 

 frequently inconceivable with reference to the present configu- 



