48 
Mr Stevenson on the Bed qf the 
which for ages past have been receiving the debris of the sur- 
rounding mountains. We must doubtless allow that they con- 
tain a smaller portion of water, or are actually of a less depth 
than they were at an earlier period of the history of the globe. 
Accordingly, from inquiries, which, in the prosecution of this 
subject, I have been led to make regarding the two last mentioned 
lakes, it has satisfactorily appeared that their waters are subject 
to overflow or rise upon their banks. On Lochlomond, in par- 
ticular, the site of a house at the village of Luss was pointed out 
to me, which is now permanently under the summer-water-mark ^ 
while the gable of another house in its neighbourhood is in dan- 
ger of being washed down by the increase of the waters of the 
loch. Whether this striking appearance is to be attributed 
wholly to natural causes, or partly to artificial operations upon 
the bed of the River Leven, flowing from the loch, I have had 
no opportunity of inquiring. But the great bench or flat space 
round the margin of the loch, which is left partly dry during 
summer, forms altogether such a receptacle for debris, as to be 
sufficient to affect the surface of the loch, and indeed permanent- 
ly to raise its waters. We also infer, though by a diflerent pro- 
cess, that the constant deposition going forward in the bed of 
the German Ocean, must likewise displace its waters, and give 
them a tendency to enlarge their bed and to overflow their 
banks or boundary. 
In this view of the subject, it will appear that we have not 
only to account for the supply of an immense quantity of de- 
bris, but we must also dispose of the water displaced by the pro- 
cess of deposition which is continually going forward at the bot- 
tom of the ocean. 
‘ With regard, then, to .the supply of the debris of which these 
banks are composed. — We find that a very great portion of it 
consists of siliceous matters in the form of sand, varying in size 
from the finest grains to coarse bulky particles, mixed with coral 
and pounded shells, the quantity of these calcareous matters 
being altogether astonishingly great; and being specifically 
lighter than the particles of sand, the shells generally cover 
the surface of these sunken banks. With regard to the vast 
collection of siliceous particles connected with the banks, our 
surprise ceases when we consider the receptacle which the North 
