The Scottish Naturalist. 197 



of land-ice than of the random and eccentric action of icebergs. 

 The researches of Swiss and French glacialists have proved that 

 during the climax of the Glacial Period an enormous area in the 

 low grounds of Eastern France was covered with a huge mer de 

 glace formed by the union of the great Rhone glacier with the 

 glaciers descending from the mountains of Savoy and Dauphiny. 

 A line drawn from Bourg by way of Chatillon, Villeneuve, Tre'- 

 voux, and Lyons to Vienne, and thence south-east by Beaure- 

 paire to the valley of the Isere, a few miles above St Marcellin, 

 indicates roughly the furthest limits reached by the mer de glace. 

 Over all the low grounds between that terminal line and the 

 mountains are found widespread sheets of boulder-clay and 

 sand and gravel, together with loose erratics. Now and again, 

 too, well-marked terminal moraines make their appearance, 

 while the rock-surfaces, when these are visible and capable of 

 bearing and retaining glacial markings, present the usual aspect 

 of roches moutonuces. The same kinds of morainic materials 

 and ice-markings may of course be followed up into the valleys 

 not only of the Alps properly so-called, but also into those of 

 the hills of Bugey and the secondary mountain-chain of Savoy 

 and Dauphiny. It has indeed long been known that local 

 glaciers formerly occupied the mountain-valleys of Bugey. A 

 number of small glaciers, for example, have descended from 

 the slopes of the mountains west of Belley (such as Bois de 

 la Morgue, Bois de Lind, &c.) to the Rhone, and again from 

 Mont du Chat to the north-west. These glaciers were quite 

 independent of the greater ice-streams of the neighbouring Alps 

 of Savoy, and the same was the case with the glaciers of that 

 mountainous tract which extends from Nantua south to Culoz, 

 between the valleys of the Ain and the Rhone. From this 

 elevated region many local glaciers descended, such as that of 

 the Valromey which flowed for a distance of some twenty miles 

 from north to south. Again, similar local glaciers have left 

 abundant traces of their former presence throughout that moun- 

 tainous belt of land that stretches between Chambery and Gren- 

 oble to the west of the valley of the Isere. The moraines of all 

 those local glaciers, charged as they are with the debris of the 

 neighbouring heights, clearly indicate that the local glaciers 

 flowed each down its own particular valley. There are certain 

 other appearances, however, which seem at first sight to contra- 

 dict this view. Sometimes, for example, we encounter in the 

 same valleys erratics which do not belong to the drainage- 



