276 BATHYMETRICAL 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 3J 

 miles, and the greatest breadth nearly half a mile. The superficial area is 

 about 776 acres, or nearly lj 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 98 J feet, or more than half 

 the maximum. 



Loch Avich was surveyed on May 26 and 27, 1903, the elevation being 

 31O85 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 west 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 100 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 Observations. During the two days devoted to the survey 

 the surface temperature varied from 50-8 to 60'l Fahr. The following 

 temperatures were taken in the deepest part of the loch at 6 p.m. on 

 May 27, 1903 : 





