922 HARRY FIELDING REID 



medial moraine, occurs in the dissipator, the moraine remains 

 on the surface of the ice ; but if the junction occurs in the 

 reservoir the moraine is covered up by later strata of snow and 

 reappears lower down in the dissipator; the further the junction 

 is above the neve-line, the further is the point of reappearance 

 of the moraine below that line. Rock material that falls on the 

 snow from the cliffs in the cirque is carried by the flow along the 

 under part of the glacier and reappears at the surface only near 

 the lower end of the dissipator. 



We have but few observations bearing on these theoretical 

 inferences. In Agassiz's map of the Unteraar glacier one or two 

 small moraines are shown as beginning on the surface of the ice 

 some distance below the neve-line. And it is not at all unlikely 

 that what is usually called the spreading of the moraines near 

 the glacier's end is largely due to the appearance at the surface 

 of the debris fallen on the glacier from the cliffs surrounding the 

 reservoir. A glance at the lines of flow (Fig. 2) will make this 

 clear. 



The Corner, the Findelen and the Zmutt glaciers, near Zer- 

 matt, end within a few miles of each other ; the first two, orig- 

 inating on high snow-covered land surrounded by snow ridges, 

 have a large portion of their surfaces comparatively clean to the 

 end ; the last, whose reservoirs are dominated by precipices 

 from which rocks are continually falling, is entirely concealed at 

 its lower end by debris. Of the tributaries of the Muir glacier 

 in Alaska, Dirt glacier, originating in a cirque, has two or three 

 miles of its lower end deeply covered by debris, whereas the 

 White glacier, nearby, whose reservoir is not surrounded by 

 cliffs, has ordinary linear moraines.^ 



The lines of flow (Fig. 2) explain why all observers have had 

 practically unsurmountable difficulties in following the stratifica- 

 tion from the reservoir through the dissipator. 



The parts of the strata formed at a distance from rocky 

 slopes have very little dust blown upon them, and consequently 

 when they reappear at the surface in the upper or middle regions 



' See Map in Studies of Muir glacier, Alaslca, Nat. Geog. Mag., Vol. IV, p. 52, 



I 



