328 Proceedings of the Royal Plujsical Society. 



Dr James Geikie reminds us that similar phenomena have 

 been recorded by geologists in Scandinavia, " cross-hatching" 

 having been observed many years ago by Forchammer in 

 Denmark, and in more recent years again and again in Nor- 

 way and Southern Sweden by various geologists. Quite 

 recently they have been detected also in North Germany by 

 Dr Penck. "The intercrossing of boulders derived from 

 different quarters," * he continues, " has likewise been fre- 

 quently noted by continental geologists in the drift deposits 

 of various parts of Europe, Perhaps among the most remark- 

 able examples are those described by MM. Falsan and Ch autre 

 in their magnificent work on the ancient glaciers of the basin 

 of the Eh one. In the region lying between Bourg and 

 Grenoble (Ain, Savoy, and Isere) the glacial deposits dis- 

 play again and again the most remarkable examples of 

 erratics which have crossed each other in their journey at all 

 angles. For example, in the neighbourhood of St Paul, a 

 little to the west of the beautiful Lac du Bourget, the glacial 

 deposits are charged with blocks of dolomitic limestone, 

 which have descended from Mont du Chat — ix., in a N.N.W. 

 direction. But in the same district occur many blocks of 

 various rocks which have come from Upper Savoy — i.e., from 

 N.E. Here the one set of boulders has crossed the other 

 nearly at right angles. And numerous other similar examples 

 are pointed out by the French glacialists. Still more striking 

 is the fact that now and again erratics have travelled in pre- 

 cisely opposite directions — one set having been carried up, 

 while another has been brought clovm, one and the same 

 valley. Thus, in the Val Eomey (S.E. of Nantua) erratics of 

 local origin may be traced south as far as the Lyons and 

 Geneva Ptailway, while boulders derived from the Alps have 

 travelled up the valley for a number of miles ! And the 

 same peculiar phenomena are repeated in the case of many 

 other valleys in Dauphiny and the adjoining regions. The 

 origin of this * intercrossing ' of erratics is very simply 

 explained by MM. Falsan and Chantre. They point out 

 that before the great glacier of the Ehone and the Arve had 



* Extract from a letter by Dr J. Geikie, F.R.S., to one of the authors of 

 this j)ap€r. 



