Oh. II.] 



EIPPLE MAEK. 



19 



cumulation of all coarse materials conveyed into deep water, especially 

 where they are composed in great part of pebbles, which cannot be 

 transported to indefinite distances by currents of moderate velocity. By 

 inattention to facts and inferences of this kind, a very exaggerated esti- 

 mate has sometimes been made of the supposed depth of the ancient 

 ocean. There can be no doubt, for example, that the strata a, fig. 7, 

 or those nearest to Monte Calvo, are older than those indicated by b, and 

 these again were formed before c ; but the vertical depth of gravel and 

 sand in any one place cannot be proved to amount even to 1000 feet, 

 although it may perhaps be much greater, yet probably never exceeding 

 at any point 3000 or 4000 feet. But were we to assume that all the 

 strata were once horizontal, and that their present dip or inclination was 

 due to subsequent movements, we should then be forced to conclude, 

 that a sea 9 miles deep had been filled up with alternate layers of mud 

 and pebbles thrown down one upon another. 



In the locality now under consideration, situated a few miles to the 

 west of Nice, there are many geological data, the details of which can- 

 not be given in this place, all leading to the opinion, that when the 

 deposit of the Magnan was formed, the shape and outline of the alpine 

 declivities and the shore greatly resembled what we now behold at many 

 points in the neighborhood. That the beds, a, b, c, d, are of compara- 

 tively modern date is proved by this fact, that in seams of loamy marl 

 intervening between the pebbly beds are fossil shells, half of which be- 

 long to species now living in the Mediterranean. 



Hippie mark. — The ripple mart, so common on the surface of sand- 

 stones of all ages (see fig. 8), and which is so often seen on the sea-shore 



Fie. 8. 



Slab of ripple-marked (new red) sandstone from Cheshire. 



