1912] STEVENSON— THE FORMATION OF COAL BEDS. 529 



it is not always possible in experiment to reproduce the complicated 

 conditions existing in nature. It is well to learn the phenomena 

 as recorded by others at some localities mentioned by Fayol. 



De Rosemont^^^ says that between Aspremont and Nice one sees 

 the great mass of pebbles marking the \'ar delta. He notes some 

 features which appear to have been overlooked by Fayol. This 

 •deposit extends northwardly to the rocks of Saint-AIartin-du-Var, 

 westwardly to Cheiron and southwardly to the sea. The homo- 

 geneous mass is 350 to 400 meters thick and plunges beneath the 

 sea between Aspremont and Cheiron with a thickness of 500 meters. 

 It is rudely stratified and the dip varies from 10 to 30 degrees. This 

 is the delta of the \'^ar, which was formed prior to the Pliocene. It 

 is cut, almost half way to the bottom, by an old valley, now filled 

 with bluish and yellowish clays, holding a Pliocene fauna. Still 

 later, this Pliocene deposit was trenched along its whole length by 

 the present river Var, which flows in a deep channel-way. The 

 phenomena described by de Rosement show that, under certain 

 relations of land and sea, the first deposit was laid down ; that under 

 other relations, the river dug for itself a broad channel-way in the 

 coarse deposit ; that under still other relations, the valley was filled 

 with Pliocene muds; and that last of all, the whole mass being once 

 more above sea-level, the river cut its way down in the muds. It 

 may well be that the steep dips referred to by de Rosemont, Lyell 

 and Fayol originated in a way different from that conceived by the 

 last two authors. 



The Aar delta, very small, was studied long ago by Martins,^^^ 

 whose investigation was extremely detailed. The stream enters at 

 Meyringen an alluvial valley, along which it meanders for about 5 

 miles, until, in approaching Lake Brienz, it divides to form a petty 

 delta, 85 meters wide at the lake shore. Coarse material is dropped 

 at Meyringen and only fine stuff reaches the lake, where it forms a 

 submerged talus. The lake is 8 miles long and a mile and a half 



^" A. de Rosemont, " Sur le delta du \'ar et la periode pluviare," Bull. 

 Soc. Geol. de France, III., Vol. V., 1877, p. 799. 



"' C. Martins, " Note sur le delta de I'Aar, a son embouchure dans le 

 lac de Brienz," Bull. Soc. Geol. de France, II., Vol. II., 1845, pp. 1 18-122. 



