264 
BATHYMETRICAL SURVEY OF 
is about 270 square miles, or ten times the area of the loch. The maximum 
depth recorded by the Lake Survey was 623 feet, while on the Admiralty 
chart of Loch Lomond a maximum of 105 fathoms, equal to 630 feet, is 
shown, but there is no indication of the level of the water at the time of 
the Admiralty survey. The volume of water contained in the loch is 
estimated at 92,805 millions of cubic feet, or over one half of a cubic 
mile ; in this respect Loch Lomond ranks second among the Scottish 
lakes, being exceeded only by Loch Ness, the capacity of which is about 
three times greater. The mean depth of the entire loch is estimated at 
only 121 J feet, less than 20 per cent, of the maximum depth, which indicates 
that a large proportion of the lake-floor is covered by shallow water. As 
a matter of tact, more than two-thirds of the lake-floor is covered by 
less than 100 feet of water, as shown in the following table, giving the 
approximate areas between the consecutive contour-lines drawn in at equal 
intervals of 100 feet, and the percentages to the total area : — 
Feet. 
Acres. 
Per cent. 
0 to 100 
11,881 
67-6 
100 „ 200 
2,880 
16-4 
200 „ 300 
974 
5-5 
300 „ 400 
528 
3-0 
400 „ 500 
450 
2-6 
500 „ 600 
767 
4-4 
Over 600 
85 
0-5 
17,565 lOO'O 
This table shows a gradually decreasing area with increasing depth 
down to the 500-feet contour, but then a striking increase in the area is 
indicated for the zone between 500 and 600 feet, compared with the two 
shallower zones, denoting that the deepest part of the loch partakes of 
a flat-bottomed character. 
The bathymetrical conditions in Loch Lomond having been so long 
known, may be here referred to briefly. The conformation of the entire 
loch is complex, but especially so in the wide southern portion, where the 
contour lines of depth are sinuous in the extreme, but even the narrow 
northern portion, which might be looked upon as a characteristic elongated 
Highland loch, is to a certain extent irregular. There are three distinct 
50-feet basins, separated by shallow water (1) at the entrance of the 
Douglas water, and (2) at the chain of islands consisting of Inchtavanach, 
Inchconnachan, Inchmoir, Inchcruim, Inchfad, and Inchcailloch, to the 
south of which chain the water is all less than 100 feet in depth. There 
are two 100-feet basins, one lying between the chain of islands mentioned 
and the entrance of the Douglas water, the other extending northw'ards 
uninterruptedly from the Douglas water delta to near the head of the loch. 
There are three 200-feet basins : a small one about a mile from the head 
of the loch having a maximum depth of 206 feet, a larger one south of 
the entrance of the Douglas water, circling round Ross point, having a 
