136 



Mr. Prestwich on the Excavation [Feb. 11, 



The small stream (the Eseardon) which joins 

 the Somme at Abbeville flows through a nar- 

 row chalk valley extending a few miles north ot 

 Abbeville. Three miles up this valley is the 

 village of Drucat ; and on the hill above the 

 village, and about 1 00 feet above the stream, is 

 a small outlier of high-level gravel which I 

 have before described, and which is remark- 

 able for the number and size of its sand- and 

 gravel-pipes penetrating the underlying chalk. 

 One of these which I measured was 22 feet 

 across at the top and 18 feet at a depth of 

 30 feet, and I estimated its depth at not less 

 than 100 feet from the surface. It was filled 

 in the usual way with sand and gravel in ver- 

 tical cylindrical layers. M. Boucher de Perthes 

 has two flint implements which are reported to 

 have come from the pit ; but I never myself 

 found any there, or any mammalian remains. 

 The sand and gravel is clean and light-coloured, 

 and very similar in character to some of the 

 beds at Menchecourt, and in so far has the 

 appearance of a fluviatile gravel, and, like it, is 

 overlain by a variable bed of loess. This bed 

 was supposed to form an isolated outlier ; but 

 on my last visit 1 found another bed, though of 

 coarser materials, on a hill of the same height 

 on the opposite side of the valley, above I'Heure. 

 The valley at the foot of the hill on which the 

 Drucat gravel is worked is about a quarter of a 

 mile wide. A lane leads direct down the slope 

 of the hill from a point near the gravel to the 

 valley ; and a roadside cutting exposes a section 

 of calcareous tufa or travertin several feet thick, 

 and containing in places numerous land shells, 

 of recent species, and traces of plants. Half a 

 mile beyond, the bed is of sufficient importance 

 to be worked for building-purposes. This bed 

 is overlain by the valley loess, and is in places 

 intercalated with it ; it commences a few feet 

 below the level of the gravel at about 70 feet 

 above the valley, and continues to near the foot 

 of the hill. 



Now it is well proved that in all purely chalk districts the line of water- 

 level proceeds from the level of the streams and rivers traversing the dis- 



