ANTIQUITY OF MAN. 413 



of undisturbed gravel, and further to show that the 

 deposit of this gravel, though referable to a compara- 

 tively late geological period, must be older than the 

 present configuration of the ground. Prestwich lost 

 no time in communicating the results of his examina- 

 tion of the Abbeville region to the Royal Society [46]. 

 He cautiously abstained from pronouncing on the antiq- 

 uity of man, contenting himself with pointing out 

 that though there could be no doubt that man was 

 contemporary with certain extinct forms of elephant, 

 rhinoceros, deer, and other animals, no evidence had 

 yet been obtained to show the chronological value of 

 the interval that had elapsed since the deposit of the 

 gravels containing the worked flints. He himself was 

 at first inclined, not so much to throw the human period 

 indefinitely backward, as to bring down the period of 

 the extinct mammalia nearer to our own day, and to 

 account for their disappearance and for the modification 

 of the superficial topography by some sudden or 

 rapid geological change, which, though transient, was 

 powerful enough to leave its memorial on the surface 

 of the land. As his investigations proceeded he felt 

 the weight of evidence continually augmenting in 

 favour of the long lapse of time required for the ex- 

 cavation of the valleys and for the production of the 

 vast changes in the configuration of the land since the 

 accumulation of the implement -bearing gravels. In 

 his next great memoir, published in 1864 [56], he ad- 

 mitted that "we must greatly extend our present 

 chronology with respect to the first existence of man ; 

 but that we should count by hundreds of thousands of 

 years is, I am convinced, in the present state of the 

 inquiry, unsafe and premature." In this valuable 

 essay, the whole evidence of the valley-gravels and of 



