154 Geological Notes on the 



current meets with, when it arrives at or near to the surface 

 of still water." Such is a brief outline of Mr Darwin's inge- 

 nious analysis of these objects, which, nevertheless, have been 

 since set down by geologists of no small repute — blinded by 

 an over-ridden theory — as the moraines of ancient glaciers. 



It happens that the truth of Mr Darwin's views is demon- 

 strated by an example of the very process which he describes, 

 now actually in operation. I may first remark, that deltas 

 are common on the borders of the Swiss lakes, and also in 

 valleys where mountain-streamlets descend to join the rivers. 

 At Alpnach, for example, near the Lake of Lucerne, there is 

 a fine specimen, a sloping, rough surface betw^een the outpour 

 of the stream from its native mountains and the river into 

 which it is received. The stream itself, in ordinary times, 

 keeps within a wide, stony channel, but in floods sweeps over 

 the whole surface, to which it thus gives shape. The great 

 plain between the Lakes of Brientz and Thun, is simply the 

 delta of the Lutschine river, here pouring towards the Aare, 

 from its source in the side vale of Lauterbrunnen. The com- 

 position of the ground, and the slight declination of the sur- 

 face from the opening of that valley towards the lakes, leave 

 no room for doubt on this point. Such a delta has been ob- 

 served in the course of formation, in modern times, on the 

 border of the Lake of Thun, where, a new opening hav- 

 ing been formed for the Kander river early in the last 

 century, there is already formed round its mouth a large 

 sloping projection of exactly this character, the process hav- 

 ing, no doubt, been hastened in this case by the abundance 

 of materials resting along the sides of the river near its 

 junction with the lake. So much for the history of the for- 

 mation of such deltas. Let us now advert to the circum- 

 stances under which they are cut down. 



The elevated Lake of Lungern, in the canton Unterwalden, 

 has been, as is well known, lowered, for economic purposes, 

 within the last sixty years. Where the head of this lake 

 formerly stood there is an assemblage of deltas, connected 

 with various mountain streamlets, the proper affluents of the 

 lake. We see these deltas, now lying high and dry, with 

 pretty sharp edges and somewhat steep cliffs a little within 



