Ch. XII.] 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, 
