48 GLACIERS 



origin, brought by the wind from great distances ; but a 

 great deal of it is dust (consisting of iron and other 

 elements), which falls on the earth from interstellar space, 

 and is called " meteoric dust." The particles are, in fact, 

 minute " meteoric stones," or " falling stars," but so small 

 and light that they do not become vapourised, or even 

 red-hot, by friction with our atmosphere. They have been 

 recognised in great quantity in the deposits on the floor of 

 the great oceans, as well as on mountain snowfields, and it 

 is estimated that a large number of tons of this " meteoric " 

 material falls every year on to the surface of the earth, which 

 must grow heavier in consequence. 



The water which is formed by the melting in summer 

 of the surface of a glacier above, and at the sides and 

 below, forms a stream, which runs beneath the glacier and 

 issues below the " snout." The snout frequently has the 

 shape of an arch overhanging a cave, from which the stream 

 issues. The water which forms by the melting of the 

 upper surface of the glacier forms streams, which often 

 grow to some size before they plunge into a crack or 

 fissure in the ice, and find their way to the rocky bed 

 below. They often wear the ice into a well-like shaft, 

 some hundreds of feet deep, and carry stones down with 

 them from the surface, which, lying on the rock at the 

 bottom, are violently rocked and driven about by the 

 falling water. Remarkable basin-like holes are thus worn 

 out in the rock-bed of the glacier, which sometimes 

 come into view when the glacier recedes, and exposes 

 the rock which it formerly covered, as in the " Glacier 

 Garden " at Lucerne. They are called " giants' cauldrons," 

 and the ice-well into which the surface-water rushes is 

 called a " moulin," or glacier mill. 



By the retreat of a glacier we are able to see other results 

 of its slow passage over the rocks, as, for instance, now at 

 the lower end of the Mer de Glace of Chamonix. The 



