18 



CAUSES OF DIAGONAL STRATIFICATION. 



[Ch. II 



The description above given of the slanting position of the minor 

 layers constituting a single stratum is in certain cases applicable on a 

 much grander scale to masses several hundred feet thick, and many miles 

 in extent, A fine example may be seen at the base of the Maritime 

 Alps near Nice. The mountains here terminate abruptly in the sea, so 

 that a depth of many hundred fathoms is often found within a stone's 

 throw of the beach, and sometimes a depth of 3000 feet within half a 

 mile. But at certain points, strata of sand, marl, or conglomerate, in- 

 tervene between the shore and the mountains, as in the annexed fig. (7), 

 where a vast succession of slanting beds of gravel and sand may be 



Fig. 7. 



Monte Calvo. 



Section from Monte Caivo to tho sea by the valley of Magnan, near Nice. 

 A. Dolomite and sandstone. (G-reen-sand formation ?) 

 a, b, d. Beds of gravel and sand, 

 c. Fine marl and sand of St. Madeleine, with marine shells. 



traced from the sea to Monte Calvo, a distance of no le6s than 9 miles 

 in a straight line. The dip of these beds is remarkably uniform, being 

 always southward or towards the Mediterranean, at an angle of about 

 25°. They are exposed to view in nearly vertical precipices, varying 

 from 200 to 600 feet in height, which bound the valley through which 

 the river Magnan flows. Although in a general view, the strata appear 

 to be parallel and uniform, they are nevertheless found, when examined 

 closely, to be wedge-shaped, and to thin out when followed for a few 

 hundred feet or yards, so that we may suppose them to have been 

 thrown down originally upon the side of a steep bank, where a river or 

 alpine torrent discharged itself into a deep and tranquil sea, and formed 

 a delta, which advanced gradually from the base of Monte Calvo to a 

 distance of 9 miles from the original shore. If subsequently this part of 

 the Alps and bed of the sea were raised 700 feet, the coast would acquire 

 its present configuration, the delta would emerge, and a deep channel 

 might then be cut through it by a river. 



It is well known that the torrents and streams, which now descend 

 from the alpine declivities to the shore, bring down annually, when the 

 snow melts, vast quantities of shingle and sand, and then, as they sub- 

 side, fine mud, while in summer they are nearly or entirely dry ; so that 

 it may be safely assumed, that deposits like those of the valley of the 

 Magnan, consisting of coarse gravel alternating with fine sediment, are 

 still in progress at many points, as, for instance, at the mouth of the 

 Var. They must advance upon the Mediterranean in the form of great 

 shoals terminating in a steep talus ; such being the original mode of ac- 



