TYLOR AMIENS GRAVEL. llU 



Somme, with escarpments as distinct and well marked as those 

 drawn of tlie Saveuse valley. 



Fig. 10. — Section three-quarters of a mile south of M. DaiWs house 

 {valley of the Arve), Loess Tein-ace. 









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jA/-^^ 





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These were steps cut in the brick-earth of the iSaveuse valley by 

 the peasants, to enable them to get up the steep sides ; but that 

 was the only information I was enabled to get as to the structure 

 of parts of these terraces, except at Longueau, where a pit was open 

 and good brick-earth visible; so I do not know their relation to the 

 chalk. At Camilla Lucy House, West Humble, near Dorking, I saw 

 a terrace cut into, sloping to the valley at 25°. The gravel was 5 

 feet thick on the face of chalk, and 7 feet thick 30 yards from the 

 escarpment. 



These terraces are of great importance to any one investigating 

 the geology of the Somme, but are not noticed by any other writer, 

 as far as I am aware. 



Y. CoifCLUSION-. 



"What the sections described in this paper plainly tell us is, that 

 the chalk vaUey of the Somme was excavated exactly to its present 

 form prior to the deposition of any of the gravel now lying in it. 

 Perhaps many layers of gravel may have been deposited and removed 

 again in this ancient chalk valley before the present gravel was 

 deposited ; but of this we cannot be certain ; so that we must take 

 the first layer of gravel covering the chalk from the higher part of 

 the section to the lower as the oldest in the section, and infer that 

 the remainder of the gravel-series was deposited in regular sequence. 

 The most delicate shells are fossilized in the river-sand of St, Acheul 

 and Montiers, just as they have been in that of Cray ford and Erith. 



This is a proof of the peaceful character of the deposition of 

 some part of the Amiens beds, just as the large flints and blocks of 

 Ores, which are so abundant among the gravel, are a proof of the 

 power of the floods which brought the coarse gravel from the pla- 

 teau, or down the rivers. If the sections near Amiens show the 

 valley-gravel continuous from a height of 200 feet, at St. Acheul and 

 the Ferme de Grace, to the Eiver Somme (coated over by a nearly 

 uniform warp of loess), and laid at a low gradient not exactly par- 

 allel to the surface of the chalk, but rather in its concavities, then 

 we must necessarily admit that the water of the Somme has at times 

 flowed over the whole surface in question from top to bottom in one 

 flood. This is not an exceptional case at all, as I should have 

 been able to demonstrate, had I been able to bring forward mj^ sec- 

 tions of other river-gravels this evening. We are all agreed that a 

 state of meteorological phenomena existed dimng the glacial period 



