188 
THE GEOLOGIST. 
caves. Eeferrring to his late exploration of Brixham Cave in 1858, the 
attention which tlie well-certified discovery of flint implements in un- 
doubted association with the remains of extinct mammalia and of reindeer 
attracted amongst geologists was remarked upon. The speaker visited 
the cave in company with Mr. Pengelly, and was much struck with the 
force of the evidence, though, for various reasons, he considered that cave 
evidence alone was not sufficient. Urged by Dr. Falconer to go and exa- 
mine the geological evidence respecting the flint implements in the valley 
of the Somme, he afterwards paid his long-intended visit to Abbeville 
(where he, on the very first day, was fortunate enough to find three 
worked flints at Menchecourt.) He was joined, on the next day, at 
Amiens, by his friend Mr. John Evans. The geological evidence, and the 
character of the flint implements, satisfied them both that here again was 
an undoubted case of contemporaneity of the works of man M^th the 
remains of the extinct mammalia. All the author has since seen on many 
subsequent visits to the Somme valley, sometimes alone, but more fre- 
quently in company with otlier geologists, has tended to confirm his first 
opinion. He then proceeded to notice some of the phenomena he had 
seen, and to give his conclusions respecting them. He had intended 
to have described the several localities in France and England at which 
flint implements had been found, but found that time would not allow his 
going beyond Amiens. This was the less important, as Mr. Lubbock had 
so recently given an able account in the same room of most of these 
places ; and his auditors were probably most of them acquainted with the 
more general account given by Sir Charles Lycll in his recent work on the 
* Antiquity of Man.' 
Mr. Prestwich then went on to describe the remarkable discovery of 
M. Boucher de Perthes, and how much honour and credit were due to 
him for his untiring perseverance, in face of general discouragement, for 
a period of twenty years, and for tv\ elve years after the publication of his 
elaborate work, ' Antiquites Celtiques et Antediluviennes.' Incited by 
this work. Dr. lligollol, an antiquary of Amiens, discovered flint imple- 
ments in great numbers near that town ; but his careful memoir on the 
subject, although it attracted the momentary attention of some French 
geologists, was allowed to drop comparatively unnoticed. Geologists ad- 
mitted the antiquity of the beds, and antiquaries admitted the workman- 
ship of the implements ; but neither would own to a conjoint interest and 
belief in them. 
Before entering upon the details of the sections, Mr. Prestwich pro- 
ceeded to make a few remarks upon the conditions under which the flint- 
implement-bearing beds were found, and how their importance and the 
time they represent were to be judged of. He observed that sea-formed 
deposits afforded massive and tangible monuments of the length of time 
required for their accumulation. But on land time passes, and builds no 
such monuments of its duration. The sand and shingle beds of a rapid 
river would be little, if at all, thicker now than a thousand years ago, for, 
instead of accumulating in the channel of that river, they are incessantly 
removed, and carried eventually out to sea, where they contribute to the 
formation of the great sedimentary deposits constantly going on there. 
The time represented by river deposits (apart from the recent silty alluvia) 
is not therefore to be measured by their thickness ; and we must not at- 
tach the less importance to the beds containing the flint implements, be- 
cause, being formed by river action, they are necessarily small, fragmen- 
tary, and superficial. But while in the sea the accn^-^'^-'' ^ — 
