Ch. XII.] 



TERTIARY STRATA AT NICE. 169 



ties nearer to Nice. From these fossils it clearly appears that 

 the formation belongs to the older Pliocene era. 



Such alternations of gravel and the usual thin layers of fine 

 sediment may easily be explained, if we reflect that the rivers 

 now flowing from the Maritime Alps are nearly dried up in 

 summer, and have only strength to drift along fine mud to the 

 sea ; whereas, in winter, or on the melting of the snow, they 

 roll along large quantities of pebbles. The thicker masses of 

 loam, such as that of St. Madeleine, may have been produced 

 during a longer interval, when the river shifted for a time the 

 direction of its principal channel of discharge, so that nothing 

 but fine mud was for a series of years conveyed to that point in 

 the bed of the sea opposite the delta. 



Uniform and continuous as the strata appear, on a general 

 view, in the ravine of the Magnan, we discover, if we attempt 

 to trace any one of them for some distance, that they thin out 

 and are wedge-shaped. We believe that they were thrown 

 down originally upon a steep slanting bank or talus, which 

 advanced gradually from the base of Monte Calvo to the sea. 

 The distance between these points is, as we have before men- 

 tioned, about nine miles, so that the accumulation of superim- 

 posed strata would be a great many miles in thickness, if they 

 were placed horizontally upon one another. The strata nearest 

 to Monte Calvo, which may be expressed by a, are certainly 

 older than those at b, and the group b was formed before c. 

 The aggregate thickness, in any one place, cannot be proved 

 to amount to 1000 feet, although it may, perhaps, be much 

 greater. But it may never exceed three or four thousand 

 feet ; whereas, if we did not suppose that the beds were origi- 

 nally deposited in an inclined position, we should be forced to 

 imagine that a sea, many miles in depth, had been filled up by 

 horizontal strata of pebbles thrown down one upon another. 



At no great distance on this coast the Var is annually seen 

 to sweep down into the sea a large quantity of gravel, which 

 may be spread out by the waves and currents over a consider- 

 able space. The sea at the mouth of this river is now shallow, 



