134 SECTION OF GRAVEL AT ST. ACHEUL. CHAP. vin. 



especially as many tusks of a hippopotamus have been ob 

 tained from the gravel of St. Roch some of these recently by 

 Mr. Prestwich ; while M. Gamier of Amiens has procured a 

 fine elephant's molar from the same pits, which Dr. Falconer 

 refers to Mephas antiquus, see fig. 19, p. 133. Hence I 

 infer that both these animals co-existed with man. 



The alluvial formations of Montiers are very instructive in 

 another point of view. If, leaving the lower gravel of that 

 place, which is topped with loam or brick-earth (of which 

 the upper portion is about thirty feet above the level of the 

 Somme), we ascend the chalky slope to the height of about 

 eighty feet, another deposit of gravel and sand, with fluviatile 

 shells in a perfect condition, occurs, indicating most clearly 

 an ancient river-bed, the waters of which^ran habitually at 

 that higher level before the valley had been scooped out to 

 its present depth. This superior deposit is on the same side 

 of the Somme, and about as high, as the lowest part of the 

 celebrated formation of St. Acheul, two or three miles distant, 

 to which I shall now allude. 



The terrace of St. Acheul may be described as a gently 

 sloping ledge of chalk, covered with gravel, topped as usual 

 with loam or fine sediment, the surface of the loam being 

 100 feet above the Somme, and about 150 above the sea. 



Many stone coffins of the Gallo-Roman period have been 

 dug out of the upper portion of this alluvial mass. The 

 trenches made for burying them sometimes penetrate to the 

 depth of eight or nine feet from the surface, entering the 

 upper part of No. 3 of the sections Nos. 21 and 21 A. They 

 prove that when the Romans were in Gaul they found this 

 terrace in the same condition as it is now, or rather as it 

 was before the removal of so much gravel, sand, clay, and 

 loam, for repairing roads, and for making bricks and pottery. 



In the annexed section, which I observed during my last visit 

 in 1860, it will be seen that a fragment of an elephant's tooth 



