GLACIERS. 675 



are intervals of rest and accumulation, and then a yielding. The 

 movement is, therefore, oscillatory, with the intervals, it may be, of 

 only a few minutes, or a few hours, or more. Such an oscillatory 

 action is especially calculated to produce a laminated structure. 

 As Tyndall has observed, the air-cells appear to have been in part 

 expelled from the bluish layers by the pressure, and in part to have 

 been obliterated by an incipient liquefaction and refreezing of the 

 layer. 



In the lower part of the glacier of the Ehone, the laminated 

 structure is produced, according to Tyndall, between the capes m 

 and n (fig. 951). It appears first in the section s, and is fully de- 

 veloped in the following one, s / . The radiating lines crossing the 

 concentric lines of tension represent crevasses. 



This lamination is very distinct over parts of most glaciers. It 

 is well shown either side of the middle of the Mer de Glace ; it 

 gives a longitudinal structure to the central portions of the Aar 

 Glacier below the junction of its two great branches, the Finster-Aar 

 and the Lauter-Aar ; it characterizes, according to Forbes, the whole 

 of the Brenva Glacier. 



2. Transportation and erosion. 



1. Transportation. — The moraines of glaciers are made from (1) the 

 stones and earth which fall from the cliffs along their borders ; 

 (2) the material received from falling avalanches ; (3) that which 

 is taken up by the ice from the surface of the valley against which 

 they move. They form in all the stages of progress of a glacier, 

 though usually the least in the region of the neve, where the peaks 

 are often small compared with the extent of snow. The surface in 

 this upper part is always peculiarly white and clean, owing to the 

 frequent falls of snow. 



From their mode of origin, it follows that moraines are situated 

 primarily along the margin of a glacier. But, when two glaciers 

 coalesce, the two uniting sides join their moraines in one ; and this 

 one is remote from the borders, and may be central — as in the glacier 

 of the Aar — if the two coalescing streams are about equal. It fol- 

 lows from the above that the number of moraines on a glacier can 

 never exceed the number of coalesced glaciers by more than one. 



In the Glacier of Zermatt, the nearest moraine in the view (fig. 

 953) is that of the RifTelhorn ; the second is a union of moraines of 

 the Gornerhorn and Porte Blanche ; the third, a union of two mo- 

 raines from two Mt. Rosa Glaciers ; the fourth, the great moraine of 

 the Breithorn, the summit in the middle of the view. Other 



