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HELMHOLTZ 



rills ripple, which carry off the water formed by the melting 

 of the ice. United, and forming a stream, they burst, 

 through a vaulted and clear blue gateway of ice, out at the 

 lower end of the larger glacier. 



On the surface of the ice there is a large quantity of blocks 

 of stone, and of rocky debris, which at the lower end of 



FIG. 104 



the glacier are heaped up and form immense walls; these 

 are called the lateral and terminal moraine of the glacier. 

 Other heaps of rock, the central moraine , stretch along the 

 surface of the glacier in the direction of its length, form- 

 ing long regular dark lines. These always start from the 

 places where two glacier streams coincide and unite. The 

 central moraines are in such places to be regarded as the con- 

 tinuations of the united lateral moraines of the two glaciers. 

 The formation of the central moraine is well represented 

 in the view above given of the Unteraar Glacier (Fie. 104). 

 In the background are seen the two glacier currents emerg- 

 ing from different valleys; on the right from the Shreck- 



