Xlll 



by his following paper, on " Les Debris de Mammiferes terrestres 

 qui se trouvent dans 1'Argile plastique aux Environs d'Epernay." 

 Though written at an earlier date, these memoirs were not published 

 until 1837. He had already, in 1833, become a Fellow of the Geological 

 Society. His memoir on the " Geology of Coalbrookdale," published 

 in the Transactions of that Society in 1836, was founded mainly on 

 visits made to Coalbrookdale in the years 1831 and 1832. This work, 

 which was accompanied by descriptions of new plants and mollusca 

 by his friend Professor Morris, was the earliest monograph on the 

 structure of a British coalfield. It at once established his reputation 

 as a geologist, and it has ever since been numbered among our 

 British classics. 



From about 1846 onwards for several years, his attention was 

 mainly concentrated upon the tertiary deposits of the London basin, 

 and he published a work on the water-bearing characters of these 

 deposits in 1851. But the scientific results of his investigations 

 were of far higher importance. He not only reduced the little 

 known English tertiaries into proper system (establishing the sepa- 

 rate existence of certain local beds to which he gave the name of the 

 Thanet Sands, proving the synchronism of the Reading beds with 

 those of Woolwich, and fixing the true position of the London clay 

 with respect to the Hampshire basin), but he succeeded in correlating 

 the tertiary beds of England, France, and Belgium in such a manner 

 that his classification was accepted by most geologists, and has stood 

 the test of time. 



This comprehensive study of the tertiary group naturally led Mr. 

 Prestwich onward to the investigation of the later and more superficial 

 deposits ; and the acquaintance which the writer of these pages had the 

 good fortune to form with him in 1851, led to an enduring friendship and 

 constant intercourse, as well as to occasional geological excursions with 

 him to spots where these drift and alluvial deposits could be examined. 

 In the winter of 1858, Dr. Hugh Falconer urged upon Mr. Prestwich's 

 attention the desirability of investigating in the field the evidences for 

 the discoveries of M. Boucher de Perthes of flint implements of pre- 

 historic man in the gravel deposits of the Valley of the Somme, which 

 were then somewhat doubtfully received, and in April, 1859, Mr. 

 Prestwich proceeded to Abbeville, where he was joined by Mr. John 

 Evans. Thence they went to Amiens, and in the gravel beds of St. 

 Acheul saw for themselves, still embedded in its matrix, one of those 

 implements of unquestionable human workmanship, the asserted 

 existence of which in the alluvial deposits had met with so much doubt. 

 The previous discoveries, thus verified and subsequently supplemented 

 by researches conducted on lines which could with confidence be 

 laid down, soon led to an entire revolution in the then existing 

 ideas as to the antiquity of man. Not that the new views were at 



