
Parr Il. Sect. ii. §5.] GLACIER TRANSPORT. 411 
so many indeed as sometimes to be covered with débris tu the complete 
concealment of the ice. At such parts the glacier appears to bea bare 
field or earthy plain rather than a solid mass of clear ice of which 
only the surface is dirty with rubbish. At the end of the glacier 
the pile of loose materials is tumbled upon the valley in what is 
ealled the terminal moraine. 
In such comparatively small and narrow ice-sheets as the present 
glaciers of Switzerland, the rock bottom on which the ice moves is 
usually, as far as it can be examined, swept clean by the trickle or 
rush of water over it from the melting ice. But when the ice does 
not flow in a mere big drain (which, after all, the largest Alpine valley 
really is), but overspreads a wide area of uneven ground, there cannot 
fail to be a great accumulation of rubbish here and there under- 
neath it. The sheet of ice that once filled the broad central plain of 
Switzerland between the Alps and the Jura certainly pushed a vast 
deal of mud, sand, and stones over the floor of the valley. This 
material is known to Swiss geologists as the moraine profonde or 
Grundmordne* (=boulder clay, till or bottom-moraine). 
When from any cause a glacier diminishes in size, it may drop 
its blocks upon the sides of its valley, and leave them there some- 
times in the most threatening positions. Such stranded stones are 
known as perched blocks (Fig. 144). Those of each valley belong to 
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Fic. 144.—View oF aN ALPINE VALLEY WITH PERCHED BLOCKS HIGH ON ITS 
Fuangs (B.). 
the rocks of that valley; and if there be any difference between the 
rocks on the two sides, the perched blocks carried far down from their 
sources still point to that difference, for they remain on their own 
original side. But during a former great extension of the glaciers of 
the northern hemisphere, blocks of rock have been carried out of 
? In 1869 I examined a characteristic section of it near Solothurn, full of scratched 
stones, and lying on the striated pavement of rock to be immediately described as further 
characteristic of ice-action. 
