Ch. XII.J STRATA AT THE BASE OF THE MARITIME ALPS. 165 



with great beds of gravel and sand, such as are now annually 

 brought down by torrents and streams in the winter, and which 

 are spread in such quantity over the wide and shifting river- 

 channels as to render the roads for a season impassable. The 

 first idea which naturally suggests itself, on viewing these plains, 

 is to imagine them to be deltas or spaces converted into land by 

 the accumulated sand and gravel brought down from the Alps 

 by rivers. But, on closer inspection, we find that the apparent 

 lowness of the plains, which at first glance might be supposed 

 to be only just raised above the level of the sea, is a deception 

 produced by contrast. The Alps rise suddenly to the height 

 of several thousand feet with a bold and precipitous outline, 

 while the country below is composed of horizontal strata, which 

 have either a flat or gently-undulating surface. These strata 

 consist of gravel, sand, and marl, filled with marine shells. 

 They are considerably elevated, attaining sometimes the height 

 of 200 feet, or even more, above the level of the sea; there 

 must, therefore, have been a rise of the coast since they were 

 deposited, and they are not mere deltas or spaces reclaimed 

 from the sea by rivers. Why, then, are the strata found only 

 at the points where rivers enter ? 



We must imagine that, after the coast had nearly acquired 

 its present configuration, the streams which flowed down into 

 the Mediterranean produced shoals opposite their mouths by 

 the continual drifting in of gravel, sand, and mud. The Alps 

 were afterwards raised to a sufficient height to cause these shoals 

 to become land, while no perceptible alteration was produced 

 on intervening parts of the coast, where the sea was of great 

 depth near the shore. 



The disturbing force appears to have acted very irregularly, 

 and to have produced the least elevation towards the eastern 

 extremity of the Maritime Alps, and a greater amount as we 

 proceed westward. Thus we find the marine tertiary strata 

 attaining the height of about 100 feet at Genoa, 200 and 300 

 feet farther westward, at Albenga, and 800 or 900 feet in the 

 neighbourhood of Nice, 



