524> Sir R. I. Murchison on the Distribution of 



transported erratic blocks, as well as from all other subsequent detritus 

 resulting from various causes which have affected the surface. He 

 first shows, from the remnants of the old water-worn alluvia which 

 rise to considerable heights on the sides of the valleys, that in the 

 earliest period of the formation of the Alpine glaciers, water, whether 

 salt, brackish or fresh, entered far into the recesses of these moun- 

 tains, which were then at a considerably lower level, ^. e. not less 

 than 2500 or 3000 feet below their present altitude. 



He next appeals to the existing evidences in the range of Mont 

 Blanc to show, that as each glacier is formed in a transverse upper 

 depression, and is separated from its neighbour by an intervening 

 ridge, so by their movement such glaciers have always protruded 

 their moraines across the adjacent longitudinal valleys into which 

 they descended — and were never united to form one grand stream 

 of ice. It is stated that there are no traces of lateral moraines 

 on the sides of the main valleys at considerable heights above their 

 present bottoms, whether on the flank of the great ridge from whence 

 the glaciers issued or on the opposite side of each longitudinal valley, 

 which must have been the case if a large mass of glacier ice had ever 

 descended the general valley. On the contrary, examples of the 

 transport of moraines and blocks across such longitudinal depressions 

 are cited from the valley of Chamonix on the one flank and from 

 the Allee Blanche and Val Ferret on the other flank of the chain of 

 Mont Blanc. Another proof is seen in the ancient moraine of the 

 Glacier Neuva, the uppermost of the valley of the Drance ; and a 

 still stronger case is the great chaotic pile of protogine blocks accu- 

 mulated on the Plan y Bceuf, 5800 French feet above the sea, which 

 have evidently been translated right across the present deep valley of 

 the Drance, from the opposite lofty glacier of Salenon. 



Having thus shown that none of the upper longitudinal and flank- 

 ing valleys around Mont Blanc were ever filled with general ice- 

 streams, the author has still less difficulty in demonstrating that all 

 the great trunk or lower valleys of the Arve, the Doire, and the 

 Rhone, oflfer no vestiges of what he calls a true moraine ; all the 

 detritus from great heights above their present bottoms exhibiting 

 either water- worn pebbles or occasional large erratic blocks, more 

 or less angular, — the latter being for the most part irregularly and 

 sporadically dispersed. As Venetz and Charpentier have attached 

 great imjjortance to the original suggestion of an old peasant of the 

 Upper Vallais,that a great former glacier alone could have carried the 

 erratic blocks to the sides of the lower valley of the Rhone, so on the 

 other hand the author relies on the practised eye of his intelligent 

 Chamonix guide Auguste Balmat, who declares that he has never 

 recognized the remains of " moraines " in that detritus of the larger 

 valleys which has been theoretically referred to glacier action. In 

 descending from the higher Alps into such trunk valleys, Sir Roderick 

 found many examples of rocks rounded on the side which had been 

 exposed to the passage of boulders and pebbles, with abrupt faces on 

 the side removed from the agent of denudation, all of them remind- 

 ing him forcibly of the storm and lee sides of the Swedish rocks over 

 which similar water-worn materials have passed. 



