236 



A NATURALIST ON THE " CHALLENGER." 



succeeding them, but in some instances it is obscured by the 

 subsequent formation of a debris slope from the falling of the 

 cliff; for the cliff, as on land, when no longer cut into by the 

 waves at its base, tends to degenerate into a slope of natural 

 inclination. 



The resemblance in the weathering of a berg by the action 

 of waves to that undergone by a rocky coast under the same 

 circumstances is complete. Caves, cliffs, pinnacle-like outliers, 

 and a shore platform at the base of the cliffs, are formed in 

 a closely similar manner in each case. 



In order that a horizontal platform of any wide extent should 

 be formed beneath the water, it is necessary that the berg should 

 float at almost exactly the same level for a very long period. I 

 do not properly understand how this occurs. Each time that a 



BI-TABULAR ICEBERG. 



At the base of the upper cliff is seen the old wash line. (From a sketch by the Author.) 



mass of ice falls from the undermined cliff in order that the 

 equilibrium should be maintained, it is necessary that nine times 

 that bulk of ice should be removed from the base. 



No doubt portions of the platforms below water are con- 

 stantly being split off by the upward pressure and floating to 

 the surface as " calves." The formation of a large platform 

 under water must, however, depend on such a " calving " not 

 taking place, unless on sides of the berg other than that on 

 which the platform is formed. Nevertheless, by some means or 

 other, either by melting or calving, a very uniform wasting of 

 the berg below water must take place in order to form a plat- 

 form. It cannot be supposed that the amount of snow which 

 lulls on the berg when set free can be sufficient to balance the 

 loss by the action of the sea. 



There must be a reason why the bergs which thus become 



