276 
BATHYMETEICAL SURVEY OF 
Loch Avich (see Plate CXXII.) lies little more than a mile to the west 
of the central part of Loch Awe, into which it drains by the river Avich. 
It is the largest loch after Loch Awe in the Etive basin, and trends east- 
north-east and west-south-west; it is narrowly triangular in outline, the 
east end forming the base and the west end the apex. The length is S~ 
miles, and the greatest breadth nearly half a mile. The superficial area is 
about 776 acres, or nearly 1| square miles, and the drainage area over 11 
square miles. The maximum depth of 188 feet was recorded in two places 
towards the eastern end. The volume of water is estimated at 3327 
millions of cubic feet, and the mean depth at 98J feet, or more than half 
the maximum. 
Loch Avich was surveyed on May 26 and 27, 1903, the elevation being 
310*85 feet above sea-level, which is identical with the level observed by 
the Ordnance Survey on March 3, 1865. The conformation of the loch is 
simple, the contour-lines coinciding approximately with the outline. The 
50-feet basin is about 3 miles, the 100-feet basin about 2J miles, and the 
150-feet basin nearly 2 miles, in length, in each case approaching closer to the 
east than to . the wesf end. One of the soundings at the maximum depth 
(188 feet) was taken a little more than half a mile, and the other about a 
mile, from the promontory called Rudha Barr na h-Earba, at the east end 
of the loch. The off-shore slope is in places very steep ; for instance, off' 
the northern shore, about three-quarters of a mile from the east end, 
soundings in 60 and 82 feet were taken close in-shore, the latter only 80 
feet off, giving a gradient exceeding 1 in 1 ; and off the south shore, where 
the Abhainn Mhor enters, a sounding in lOO feet was recorded about 120 
feet off-shore, indicating a gradient of nearly 1 in 1 ; and at the extreme 
east end a sounding in 102 feet was taken comparatively close in. 
The approximate areas between the contour-lines drawn in at equal 
intervals, and the percentages to the total area, are as follows : — 
Feet. 
Acres. 
Per cent. 
Oto 50 
230 
29-6 
50 „ 100 
144 
18-6 
100 „ 150 
185 
23*8 
Over 150 
217 
28-0 
776 
.100-0 
The flat-bottomed nature of the basin, giving the well-marked U-section 
characteristic of glacier-eroded rock-basins, is strikingly shown by the 
large areas of the deep-water zones, especially of the deepest zone of all, 
which is nearly equal to the shore zone, although the interval between the 
150-feet contour and the greatest depth is only 38 feet as compared with 
50 feet for the other zones. 
Temperature Ohservcitions.--V)mmg the two days devoted to the survey 
the surface temperature varied from 50°*8 to 60°*1 Eahr. The following 
temperatures were taken in the deepest part of the loch at 6 p.m. on 
May 27, 1903 
