9 



three French centimetres. This rate of increase, if one could 

 fairly adopt such a ehrononietric scale, would demand many 

 thousands of years for the formation of thirty feet. " Small as 

 is the progress hitherto made in interpreting the pages of the 

 peaty record, their importance in the valley of the Somme is 

 enhanced hy the reflection that whatever he the number of 

 centuries to which they i-elate, they belong to times i)osterior to 

 the ancient implement bearing beds which we are next to 

 consider, and are even separated from them as we shall see, l>y 

 an interval far greater than that which divides the earliest 

 strata of the peat from the latest."' Immediately underlying 

 the peat in the bottom of the valley and recumbent on the 

 chalk, is a gravel bed, l)elieved to be the most recent of the 

 gravel deposits, formed from the wreck of older gravels to be 

 described presently, and formed during the last hollowing-out 

 and deepening of the valley innnediately before the connnence- 

 ment of the growth of peat. 



We come now to the implement bearing deposits, the older 

 gravels formed on the sides of tlie hills l)ounding the valley at 

 different heights.. The Ih-st series of these is found at levels 

 slightly elevated above the i^resent river The lowest bed of 

 this series in which the implements are found, consists of gravel 

 mixed with marl and sand, and contains fresh water, land, and 

 in some of the lower sands, marine shells, showing that the 

 river at this part was sometimes gained upon by the sea. This 

 bed is about twelve feet in thickness. Overlying this is about 

 fifteen feet of loam, containing fresh-water and land shells, and 

 the bones of elephants. Of the shells fomid in this series a 

 small proportion are of extinct si)ecies. The species of gravels 

 next described, and the oldest in which tlint implements are 

 found, is a series similar in structure to the above, and found 

 at a height o><e hwidrfd feet above the present level of the 

 river. In the Huviatile deposits overlying both thest^ gravel 



