404 Proceedings of the Royal Society 
Teith. Along our Scottish rivers there are similar high gravels, 
80 feet or more above the stream ; and it is known that, pre- 
viously to the time of their formation, the rocky structure of our 
valleys had already been hollowed out nearly as deep as now. This 
is shown at Kingussie, where the 70 feet terrace — and at Crom- 
dale, where the 80 feet terrace — are seen resting on the rock 
nearly on a level with the river-bed. If, then, with the rocky 
bed down on its present level, the Scottish streams have managed 
somehow to form those high-lying deposits, why may not the French 
rivers have done the same ? In that case, the Somme would re- 
quire no time for the subsequent excavation of its valley, and the 
human period, so far as this argument is concerned, may not he so 
long after all. 
The force of this does not depend on the correctness of the views 
stated above as to the formation of these terraces. Whatever was 
the way in which the Scottish rivers went to work, it was after the 
rock had been excavated, and the question would still be, why may 
not the French rivers have done the same ? 
One point seems clear, that the case of the French gravels must 
be shown to differ from those of Scotland before the advocates of 
extreme antiquity can prove their case from the Somme. After 
admitting the case in Scotland, if a distinction is to be made in 
regard to France, the burden of proof will lie with them. The 
probabilities would certainly seem to be against them. Rivers 
and valleys have the same laws in different countries. If the 
French rivers be alleged to have acted differently from the Scottish 
it may have been so, but the grounds of the difference would need 
to be adequate, and the proof clear. In the present case, the 
alleged distinction has reference altogether to the excavation of 
the rock. In France, they say it had to be done subsequently to 
the time of the terraces ; in Scotland, it must be admitted to have 
been done before. Are there any grounds on which such a distinc- 
tion can be made good? Was there such a difference in the for- 
mation of valleys between Scotland and France? 
It wdll not be alleged that the soft texture of the chalk rock 
of the Somme, as contrasted with our harder rocks, can form the 
ground of distinction. In France itself the same valley-systems 
traverse many different kinds of rock. 
