403 
of Edinburgh, Session 1870—71. 
Upper Earn, and of the terraces of Loch Lubnaig with those of 
Loch Earn, as formerly explained.* It is confirmed by the terraces 
of the Spey, and more especially by the failure of all the other ex¬ 
planations. 
Our knowledge of this whole series of deposits is as yet far too 
imperfect to allow of anything like a complete theory of their for¬ 
mation. If a suggestion might be offered, perhaps the course of 
events may have been something like this. When the glacial 
epoch ended, and the covering of ice and snow melted off Scotland, 
there would be no small amount of debris over the face of the coun¬ 
try, and, unprotected by vegetable covering, it would be washed 
down into the valleys. Every one admits that the rivers of that 
age were larger than now—how much larger it is difficult to say. 
If the Spey had five times its present volume (as Mr Prestwich 
suggests in the case of the Somme) it would, judging from the 
present force of its current, assuredly keep its central channel open 
whatever the amount of debris which came down into the valley. 
Biver-like, it would form its banks, and spread out its haughs up to 
the height to which its floods could rise, when confined to its com¬ 
paratively narrow channel. In the case supposed that height may 
have been great; and these old high terraces may be the fragments 
of alluvial platforms, which once spread out along the valley, where 
the old floods had raised them. Before the whole facts are fully 
explained, it seems probable that our ideas of the amount of water 
present in these old floods may have to be enlarged. 
The bearing of these facts on certain arguments for the an¬ 
tiquity of man was considered, with special reference to the Spey 
deposits. There are gravel beds along the Somme in France, 
which, up to the height of 80 feet, contain flint weapons, 
which are held to be of human manufacture; and the argument 
is, that the river has excavated through the rock the valley in 
which it now flows—that this has been done since the deposition 
of the gravels, and to allow time for such excavation their age, and 
consequently the human period, must be carried back into some 
vast antiquity. 
But here is an important fact, which the deposits of the Spey 
make still more clear in some respects than those of the Earn and 
* Trans. Royal Soc. Edin., vol. xxvi, 168-166. 
