1844.] NEW DISCOVERY RESPECTING THE DIRT BANDS. 39 



strata of the Neve ; viz. (1.) the structure assumed by the ice 

 of the Talefre is extirpated entirely by its precipitous descent 

 to the level of the Glacier de Lechaud. where it reappears, or 

 rather is reconstructed out of the bruised fragments, according 

 to a wholly different scheme ; (2.) the veined structure often 

 cuts the medial moraines, i.e., a glacier composed of two, 

 having originally distinct looped structures, assumes finally, after 

 being for some time united, a single looped structure. 



From the heights above the Egralets, which command a 

 most extensive bird's-eye view of nearly the whole Mer de 

 Glace, about 2000 feet below, I was led to make a very inte- 

 resting observation, on the whole, the newest of the season. 

 I need not remind your Lordship, that I first observed, in 1842, 

 the existence of certain wave-like marks on the surface of the 

 Mer de Glace, figured in my map of that year, and represented 

 in the models submitted to the Royal Society last winter. These 

 waves, or " dirt-bands," as I termed them, were parallel in their 

 course to the veined or ribboned structure of the ice, and 

 recurred at pretty regular intervals upon the surface of the 

 glacier, the loops pointing in the direction of its motion, at 

 an average distance, as I think, of between 600 and 700 feet. 

 (The exact value is stated in my book.)* I was prevented, by 

 a premature fall of snow, from tracing these bands (which I also 

 termed " annual rings") higher up on the glacier than the point 

 called Trelaporte. Standing, on the 12th September last, above 

 the precipices of the Couvercle, at the foot of the Aiguille du 

 Moine, as above mentioned, I not only saw with admirable dis- 

 tinctness the " dirt-bands" between Montanvert and Trelaporte 

 delineated, as it were, upon a plan ; but I was enabled to count 

 six new ones higher up in the direction of the Glacier du 

 Geant. Then followed a space corresponding to three intervals 

 of dirt-bands, which were, however, not perceptible. Higher 

 up, on the Glacier du Geant, was a most striking and beautiful 

 appearance, quite new to me. The heavy snow of the previous 

 winter had not been entirely melted during the whole summer, 



* [711 feet, Travels, 1st Edition, p. 165.] 



