Occurrence of Stoties on the surface of Glaciers. 175 



that the stones " are actually introduced into the ice by fric- 

 tion at the bottom of the glacier, and forced upwards by the 

 action of the frontal resistance which produces the frontal 

 dip of the veined structure, and that they are finally dis- 

 persed on the surface by the melting of the ice." 



There is scarcely any geologist conversant with the phe- 

 nomena of the glaciers, who could be satisfied with this ex- 

 planation. I shall endeavour to shew that the appearance of 

 stones at the surface is obviously the consequence of the pri- 

 mitive stratification in the upper parts of the glacier. 



Let the diagram be the longitudinal section of one of our 

 large glaciers, — the Glacier du Rhone, for example. Like 

 all the large alpine glaciers, its greatest thickness is pro- 

 bably at its beginning ; but, in consequence of the annual 

 mcltinsr, it becomes more and more reduced as it advances. 

 In order to supply its place, a new stratum of snow is an- 

 nually deposited at its origin, and in the mean time a certain 

 quantity of rocks fall down on it from the neighbouring moun- 

 tain slopes X. The next winter this layer, with its debris, will 

 be covered by a new stratum ; and if there were no melting, 

 and if the motion were equal in all the parts of the glacier, 

 this debris would remain buried (below the^dotted horizontal 

 line), and be for ever concealed in the interior of the glacier. 

 But w^e know that a certain amount of ice is melted every 

 year from the surface of the glacier, and in consequence of 

 this, the debris become by and by discovered. The first will 

 appear at the outcropping of the stratum a. Little farther 

 below another boulder will come forth out of the layer b, an- 

 other, again, out of the layer c, and so on, till they become so 

 numerous that they form regular tracks. Beautiful examples 

 of this appearance of stones and moraines are shewn in the 

 map of the Glacier de I'Aar, in M. Agassiz' new work, to 

 v/hich I refer for more ample information on this subject. 

 This appearance aff^ords us, after all, the most striking evi- 



