Professor J. Prestwich, D.C.L., F.R.S. 243 
Belgium. Mr. Prestwich showed, on the evidence of their organic 
remains, that the Thanet Sands were the equivalent of the lower 
Systeme Landenien of Dumont, whilst the Woolwich and Reading 
beds corresponded with the upper Landenien; the London Clay with 
the Systéme Ypresien; the Bracklesham Sands with the Systeme 
Bruzxellien; and the Barton with the Lackénien. In the Paris basin, 
Mr. Prestwich could not recognise the Thanet Sands, but considered 
that the marine sands of Bracheux, which also repose on the Chalk, 
were the equivalent of the lower estuarine sands of Woolwich, and 
of the more entirely marine green sands of Richborough; and he 
further showed that the sands under the Physa beds at Rilly should 
be referred to the same zone, whilst the Physa bed itself he con- 
sidered to be a local deposit intercalated in the lower part of the 
same Woolwich series—a conclusion contested, at first, by the 
French geologists. The London Clay he placed approximately on 
the level of the Sables Coquilliers of D’Archiac, whilst the Calcaire 
Grossier, before referred to the London Clay, was identified by him 
with the middle Bracklesham and Bagshot Sands; and the Barton 
beds with the Sables des Beauchamp. 
In the meantime, Mr. Prestwich’s attention had been directed to 
the more recent superficial or Quaternary deposits, and it was while 
engaged on these that the discoveries of M. Boucher de Perthes 
relating to the paleolithic flint implements attracted his notice. 
These discoveries had been known to geologists, as were those 
relating to analogous discoveries elsewhere in caves, for many years ; 
but they failed to satisfy geologists, and were received with in- 
eredulity both in England and France. 
Mr. Prestwich had been intending for some years to examine the 
evidence personally, but it was not until 1859, at the instigation of 
his friend, the late Dr. Hugh Falconer, who had long held the same 
views with respect to the probable antiquity of man, that he was 
able to undertake the investigation of the drift deposits of the 
Valley of the Somme. By this tnquiry to which he invited the 
codperation of Sir John Evans, Godwin-Austen, and other geo- 
logists, he quite satisfied himself and them that the flint implements 
were the work of man, and that they were lying in undisturbed beds 
of sand and gravel, in conjunction with the remains of extinct 
mammalia, as had been asserted by Boucher de Perthes and Dr. 
Rigollot; and his paper before the Royal Society at once gained 
acceptance for his views amongst geologists. 
Mr. Prestwich, in a subsequent paper, showed that the flint imple- 
ments occurred on two or more levels, which he designated as the 
‘‘high- and low-level valley gravels,” and that the former were 
formed and deposited before the excavation of the valley in which 
they occurred, and therefore vastly extending the antiquity of these 
deposits. The loess with which these gravels were associated was 
shown not to be the result of one flood or of lakes, but to belong to 
different stages of the formation of the valley; to be, in fact, a silt 
deposited during floods of the old rivers at several periods of their 
existence. 
