502 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jime 3, 



of the high-level gravels (low- water level, fig. 3) to that of the low- 

 level gravels (on and below the sea-level, fig. 6). 



In this particular case the shell-evidence is wanting, but I pur- 

 pose to show that, notwithstanding a certain difference, the beds at 

 Moulin Quignon can be correlated with those of St. Acheul, whilst 

 both have been already shown to hold the same relative position to 

 the modern river, or to be about 100 feet above its present level. 

 Fig. 1 represents the section of the gravel-pit at the former place. 

 The stratification is rude, the beds contorted, and the seams of sand 

 are subordinate. The upper bed (a) consists of a coarse brick-earth 

 full of fragments of flint, mostly white and angular, but mixed with 

 some subangular gravel. The under surface of this bed is very 

 irregular, and it often descends in funnel-shaped cavities down into 

 the body of the gravel. If we eliminate the variable ingredients (i. e. 

 the subangular gravel) from this bed, the residue will be found to be 

 identical with the coarser bed of brick-earth which overlies the flu- 

 viatile beds at St. Acheul (fig. 2, a), and which also contains a variable 

 proportion of angular flints peculiar to it, and of subangular gravel 

 derived from the underlying beds. These upper beds I would there- 

 fore refer to one and the same cause, and consider as local variations 

 of Loess. The section I have given of the gravel-pit at St. Acheul 

 (fig. 2) represents the different beds in their least disturbed state, but 

 the contact between the Loess and the fluviatile beds is at places as 

 irregular as at Moulin Quignon. The same variations exist in the 

 lower fluviatile beds. At Warean's pits, St. Acheul, the beds of sand 

 (6) have almost entirely disappeared, no Shells are found, and the 

 gravel is as coarse and irregular as at Moulin Quignon, and with only 

 occasional seam of sand. At Moulin Quignon itself, however, the 

 beds of sand are always most developed in the upper part of the sec- 

 tion, and sometimes they there replace the gravels for a short distance. 

 In both places the intercalated seams of sand occasionally show oblique 

 bedding, none of the beds are persistent, the grains of quartz are 

 worn and rounded, and the bulk of the flints subangular. The dif- 

 ference of colour is one of no importance, that being for the most 

 part a change subsequent to the deposition of the beds. In all the 

 physical conditions there is, therefore, an agreement between the 

 beds at St. Acheul and Moulin Quignon. The presence of organic 

 remains in all gravels of this age is of very local occurrence. 

 Although scarce, remains of the Elephant have been occasionally 

 found at Moulin Quignon, whilst teeth of the Horse and Ox have 

 been found at the adjacent pit of St. Gilles. 



On the opposite side of the valley is Mautort, and on the slope of 

 the hill above the village is a deposit of gravel presenting the same 

 general characters as that at Moulin Quignon, and overlain by a bed 

 of Loess, which is here, however, well marked and developed. JN T o 

 Shells are found, but some of the seams of gravel have a more sandy 

 and fluviatile appearance than at Moulin Quignon, arising probably 

 from a somewhat greater depth of water ; for the level of this bed 

 is about 10 to 15 feet lower than that of Moulin Quignon. In all 

 probability we have in both these places part of the bed of the old 



