CONTAINING FLINT IMPLEMENTS, AND ON THE LOESS. 
251 
more ready explanation. I long since had proposed the separation of the gravels into 
the high-level gravels and low-level gravels, and shown that the former were older 
than the latter. I was, however, at one time disposed to adopt in part some of the 
views of M. Elie de Beaumont with respect to the operation of cataclysmic action in 
preference to the slower action of rivers ; but further research, and the discovery of 
land and freshwater shells in so great a number of low-level gravels, and in some of 
the high-level gravels, and especially the striking evidence eventually afforded by the 
beds of St. Acheul, and by the higher-level gravels around Paris*, satisfied me that 
river-action peculiar to each valley commenced with the high-level gravels, while the 
mass of debris and the large blocks present in the beds indicate the action of a large 
volume of water and of ice-transport. Further, I was ultimately led to connect the 
Loess with both series of valley-gravels, and the frequent independence of the former, 
which at first seemed an irreconcileable difficulty, finally proved an important auxiliary 
fact ; for the separate range of this deposit now serves as a measure of the old flood 
waters, and of the extent of the river inundations during this quaternary period. 
I conceive that the hypothesis brought forward in this paper gives consistency to the 
whole subject. It brings down the large mammalia to a period subsequent to that when 
the extreme glacial conditions prevailed, and closer to our own times ; it places all the 
old river alluvia in the same period, and groups together the previously isolated fluvia- 
tile beds of Grays, Brentford, and other places in England, together with the Loess 
and various “ Sables lacustres ” and “ diluviums ” (part) of the French authors ; it con- 
nects the great platform terraces of gravel skirting so many of our river-valleys with 
the same period, and makes the connexion between these, and the excavation of the 
valleys themselves and the formation of the Loess, dependent upon one prolonged and 
uniform set of operations, in accordance with the climatal conditions and necessarily 
resulting from them. — May 1863. J 
§ 2. GEOLOGICAL POSITION OF THE FLINT-IMPLEMENT-BEAKING BEDS. 
In almost every instance the flint implements have been found in beds of sand and 
gravel along the line of existing river- valleys, — in some cases but little above the level 
of the rivers, in others on adjacent hills at heights of from 30 to 100 feet above the 
river. In these valleys one series of gravel-beds is spread over more or less of their 
breadth, rising occasionally on their flanks to a height of 10 to 30 feet, and ranging 
throughout their length, though constantly obscured and hidden by recent alluvial 
deposits. The lower ranges of hills which flank these valleys on either side are occa- 
sionally capped by other similar gravels, but which, so far from being continuous like 
the lower-level beds, occur only at intervals, and there are long tracts without any such 
drift. The higher gravels are also generally separated from the lower gravels by a bare 
sloping surface, whilst they rarely extend far from the valley and never reach the tops 
* This evidence is, with a few rare exceptions, wanting in the high-level gravels of England. 
