xiii
by his following paper, on " Les Débris de Mammifères terrestres
qui se trouvent dans l'Argile plastique aux Environs d'Épernay."
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 tho
structure of a British coalfield. It at once established his reputation
as a geologist, and it has ever since been nunbered 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 excursious 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
