808 THE 'JOURNAL OF GEOLOGY. 



Then it falls ten feet, and, curving a little to the west, rises thirty 

 feet to where it reaches its greatest elevation, one hundred and 

 fifty feet above mean tide. This is also the elevation of the 

 front of the sand-plain. At this point it breaks up into several 

 more or less clearly defined branches, which distribute the sand 

 to build up the delta in the estuary. 



These branches fall off in height towards the head of the sand- 

 plain, as is often seen in similar deposits elsewhere. As it has been 

 shown that the amount of post-glacial erosion has been small, 

 this depression must be due to conditions existing while the ice 

 was present. The first model shows a large kettle now occupied 

 by a pond which lies north of the sand-plain and east of the 

 esker. This depression, being filled with ice after the course of 

 the esker river was changed, must have had an outlet, and as the 

 main body of ice would have prevented the formation of an out- 

 let on the north, it seems reasonable to suppose that this water 

 quietly cut through a slight sag in the esker to the west. This 

 cutting would have continued until the ice-sheet had retreated 

 farther north, and the ice block in the kettle had melted, and its 

 depth would be governed by the amount of the lowering of the 

 water in the estuary, caused by rising of the land. 



Two branches from near the north end of the esker run into 

 cusps at the head of a second smaller sand-plain deposit, formed 

 when the ice-front had retreated some two thousand feet, and 

 while the ice remained at this second point there would have 

 been no outlet for the water to the north. The frontal lobes of 

 this second sand-plain are not at all typically developed. 



7. Delta streams. — In front of the openings of the esker tun- 

 nels will be seen the depositing streams breaking up into many 

 branches, as Professor Russell has described them in Alaska 1 . 

 Some of them are represented as having already ceased to 

 flow to the edge of the delta, and are fast filling up ; others 

 are pushing out their resulting lobes as far as they can reach ; 

 while a third class are supplying detritus to those in front, and 

 are building up their channels to give themselves greater carry- 



1 See Malaspina Glacier, page 238. 



