336 SCIENCE PROGRESS 



terminal moraine. Here an ancient glacier of the Iller came 

 to an end. 



A question of capital interest now presents itself: what are 

 the relations, if any, between the terrace and the moraine ? 



The answer to this has been given by Penck, who has shown 

 that the river terrace loses itself in the moraine ; the two meet 

 and interdigitate with each other, as shown in the diagram 



(fig- i). 



Where the glacier gave birth to a river, there the moraine 



passes into a terrace. 



As there are four terraces, so there are four moraines, one 

 to each terrace. 



A consideration of these facts leads to very important con- 

 sequences. In attempting an explanation let us begin with the 

 first or highest terrace. To account for the formation of the 



Terminn.1 Mar&lrvs- 

 SchoCCer 



Fig. i. 



thick sheet of shotter it represents, we must assume the 

 existence of a river, so heavily overburdened with detritus, that 

 it had little or no power to erode ; it could carry away the 

 material of the moraine, round the angular fragments into well- 

 worn pebbles, and distribute them far and wide over its valley 

 floor, but it could not deepen its channel. Its energy was re- 

 stricted to building up a sheet of shotter, over a hundred feet 

 in thickness, which stretched from side to side of the river 

 valley. This sheet of shotter represents the first stage in the 

 formation of the terrace (a, fig. 2). 



Of the sheet so formed only the first terrace, a mere remnant, 

 a narrow selvage, now exists, lining the side of the valley : 

 the river which previously deposited it has since carried the 

 greater part of it away. It seems natural to assume that the 

 river had acquired a higher degree of activity, probably as a 

 consequence of increased volume and velocity; and its enhanced 

 power is still further shown by the fact that after removing the 

 shotter it was able to wear its way down into the harder rocks 



