78 
BATHYMETRICAL SURVEY OF 
A series of temperatures beneath the surface was taken in the deepest 
part of the loch on May 17, at 5 p.m., with the following results : — 
Surface .. 
5 feet .. 
10 „ .. 
20 „ .. 
30 ,, .. 
50 , , . . 
100 ,, .. 
125 „ . 
150 ,, .. 
200 „ .. 
250 ,, ... 
43° 
43° 
43° 
43° 
43° 
43° 
43° 
42° 
42° 
42° 
41° 
8 Fahr. 
5 „ 
4 „ 
3 „ 
2 ,, 
2 „ 
1 
3 „ 
1 „ 
0 „ 
This series shows a range of 2°-3 between the temperature at the 
surface and that at 250 feet, the greatest fall being one of 0°’8 between 
100 and 125 feet. 
Loch Tummel (see Plate XXIII.). — Loch Tummel is situated amid 
beautiful scenery, rock, wood, and water being combined in such a way 
as to present pictures of rare loveliness, the crests of Farragon, Meall 
Tarruinn Chon, and Schiehallion rising to great heights to the south 
and south-west. It contains large trout and a great many pike. Loch 
Tummel is two and three-quarter miles in length, with a maximum 
breadth of half a mile, the mean breadth being a little over one-third 
of a mile, or 13 per cent, of the length. Its waters cover an area of 
630 acres, or rather less than one square mile. It drains directly an 
area of 62^ square miles, but since it receives the outflow from Lochs 
Pannoch, Laidon, Ba, &c., its total drainage-area is about 306 square 
miles, or 312 times the area of the loch. Nearly 300 soundings were 
taken in Loch Tummel, the maximum depth observed being 128 feet, or 
4 feet more than the maximum depth recorded by Mr. Grant-Wilson, 
who took 123 soundings in 1888. The volume of water contained in the 
loch is estimated at 1,316,635,000 cubic feet, and the mean depth at 
48 feet, or 37 J per cent, of the maximum depth. The length of the 
loch is 113 times the maximum depth, and 302 times the mean depth. 
The floor of Loch Tummel is irregular, falling into three deep basins 
separated by two ridges, the maximum depth on the westerly ridge 
being 52 feet, and the maximum depth on the easterly ridge being 56 
feet. The deepest of the three basins is situated near the west end of the 
loch, the maximum depth of 128 feet occupying a central position in this 
basin, but a short distance to the south a sounding of 74 feet is recorded 
in close proximity to a sounding of 127 feet. The 100-feet contour-line 
in this western basin is almost circular and nearly one-third of a mile in 
diameter ; about one-fifth of a mile to the east is an isolated sounding 
of 102 feet, surrounded by shallower water. The central 100-feet basin 
is oblong in outline and nearly half a mile in length, the maximum 
