THE FRESH- WATER LOCHS OF SCOTLAND. 339 



observed in a central position, but nearer to the eastern than to the 

 western end of the loch. The volume of water is estimated at 1435 

 millions of cubic feet, and the mean depth at over 65 feet. The loch 

 was surveyed on October 6, 1903, but the elevation of the lake-surface 

 above the sea could not be determined by levelling. The water in the 

 loch was very high on the date of the survey, the level then being 

 estimated at about 703 feet above sea-level, but the normal level .is 

 probably about 700 feet. 



Loch Beinn a' Mheadhoin is rather complex in conformation, in- 

 cluding as it does three deep basins separated by shallower water. 

 Near the western end of the loch is a small basin having a maximum 

 depth of 95 feet, and near the eastern end is a larger basin having a 

 maximum depth of 117 feet, while the largest and deepest basin occupies 

 the central portion. The two ridges separating these three basins may 

 be due to the deposition of material brought down by the streams 

 entering the loch at these places along the northern shore, of which 

 the westerly stream (Amhainn a' Ghlinne Fhiadhaich) is the more 

 important; the maximum depth observed on the western ridge was 

 69 feet, and on the eastern ridge 97 feet. The 25-feet and 50-feet 

 contours are continuous from end to end of the loch, while the 75-feet 

 contour is broken at the position of the western ridge, and the 100-feet 

 contour is broken at the position of the eastern ridge. The eastern 

 100-feet basin is nearly half a mile in length, and the main 100-feet 

 basin nearly 1| miles in length; within the last-mentioned basin is a 

 long, narrow 150-feet basin, based on soundings of 159, 167, and 154 

 feet, with an isolated sounding in 156 feet a quarter of a mile farther 

 west. It seems doubtful whether this isolated sounding may not be 

 connected with the principal basin by deep water, and in that case the 

 150-feet basin would be nearly a mile in length. The deepest sounding 

 in 167 feet was recorded about a mile from the eastern end of the loch, 

 and about H miles from the western end. The cross-section C-D, in 

 this position, shows a steeper gradient off the northern than off the 

 southern shore; but the soundings, as a whole, afford no evidence of 

 any very steep slopes. The deeper part of the loch has quite a flat- 

 bottomed character, as indicated by the figures in the following table, 

 giving the areas between the consecutive contour-lines : 



to 25 feet 98 acres 19 '5 per cent. 



25,, 50 80 15-8 



50,, 75 96 19-0 



75 100 174 34-5 



Over 100 , 56 . 11-2 



504 , 100-0 



It will be observed that the largest zone is the one between 75 and 

 100 feet, and that the area of the lake-floor covered by less than 50 feet 



