FIG. 2 . LONGITUDINAL SECTION OF LOCH KATRINE, ALONG THE AXIS OF MAXIMUM DEPTH. THE BLACK PORTION SHOWS THE TRUE 
slopes; the outline shows the slopes exaggerated TEN TIMES. 
THE FRESH- WATER LOCHS OF SCOTLAND. 
3 
FIG. 3 . CROSS-SECTION OF 
LOCH KATRINE. THE 
BLACK PORTION SHOWS 
THE TRUE SLOPES ; THE 
OUTLINE SHOWS THE 
SLOPES EXAGGERATED 
TEN TIMES. 
The bulk of water con- 
tained in the loch is esti- 
mated at 27,274,000,000 
cubic feet, or about one- 
fifth of a cubic mile, and 
the mean depth (suppos- 
ing the loch to be of 
uniform depth over its 
present area) at 199 feet 
(33 fathoms), the mean 
depth being over 40 per 
cent, of the maximum depth. The length of the 
loch is 85 times the maximum depth, and 211 
times the mean depth. 
The surface of the loch is, according to the 
Ordnance Survey maps, at an elevation of 364 
feet above sea-level, so that our survey shows 
that a considerable portion of the bottom of 
the loch (equal to about 645 acres, or over one 
square mile) lies below sea-level, the deepest part 
being 131 feet (or 22 fathoms) below the level 
of the sea. The area below the level of the 
sea is indicated by a red line on Plate IV. In 
this respect Loch Katrine differs from the other 
lochs referred to in this paper, for in none of them 
is the depth sufficiently great to bring any portion 
of their bottoms below the level of the sea. 
The soundings show that Loch Katrine prac- 
tically forms a single basin, not being divided, like 
Loch Lomond and Loch Lubnaig, for instance, 
into separate basins by any important ridges or 
rises on the bottom. The deepest part is in the 
centre of the loch, a long narrow depression, with 
depths exceeding 400 feet, extending for over 4 
miles from opposite Coilachra to opposite Huinn 
Dubh-aird, with a maximum width of over a quar- 
ter of a mile ; this 400-feet depression has an area 
of about 515 acres, or 17 per cent, of the entire 
superficial area of the loch. The deepest sounding 
(495 feet) is situated at the very eastern extremity 
of the 400-feet depression. 
The 300-feet depression is over 5 miles in 
length, with a maximum breadth of one-third of a 
mile ; it extends from off Coilachra to near Ellen’s 
isle. The area enclosed between the 300-feet and 
