THE FRESH-WATER LOCHS OF SCOTLAND. 
91 
in outline, somewhat resembling the capital letter Y, a promontory of 
land projecting into the loch from the eastern shore opposite the inlet 
on the western shore which leads to the outflow. The length of the loch 
from north-east to south-west in a straight line is about half a mile, but 
a line following the axis of deep water would be considerably over half 
a mile in length. The maximum breadth is about one-third of a mile, 
and the mean breadth about one-seventh of a mile. Its waters cover 
an area of about 43 acres, and it drains an area twenty times greater, 
or about IJ square miles. About 60 soundings were taken in Lochan 
Breaclaich, the maximum depth observed being 41 feet. The volume of 
water is estimated at 26,619,000 cubic feet, and the mean depth at 14 
feet, or 34 per cent, of the maximum depth. The length of the loch is 
64 times the maximum depth, and 187 times the mean depth. The 
bottom of the loch is fairly regular, sinking, to the north and south of 
the promontory referred to, into two basins with depths exceeding 25 
feet, occupying the arms, as it were, of the letter Y, while the shank of 
the letter, leading to the outflow, is occupied by shallower water. Of 
the two deep basins the northern one is the larger and deeper, the 
maximum depth of 41 feet having been found approximately in the 
centre of this basin, but towards the north-western shore, while the 
southern basin is based upon soundings of 32 and 26 feet. The 10 -feet 
basin is a continuous area extending from close to the north-eastern end 
to near the south-western end, and occupying the greater portion of the 
loch. The area of the lake-floor covered by less than 10 feet of water is 
over 19 acres, or 45 per cent, of the total area of the loch, while that 
covered by more than 10 feet of water is nearly 24 acres, or 55 per cent. 
Lochan Breaclaich was surveyed on June 16, 1903, but the elevation of 
its surface above the sea could not be determined. 
T emperature Observations . — The temperature of the surface water 
on commencing the survey at 2 p.m. on June 16, 1903, was 57°'0 Fahr. 
Serial temperatures taken in the deepest part of the loch gave the 
following results:- — 
Surface ... 
57° ‘5 Fahr 
5 feet ... 
57° -5 ,, 
10 „ ... 
57° -4 „ 
15 ,, ... 
51°-2 ,. 
20 „ ... 
49° -3 
40 ,. ... 
48° -0 „ 
It will be observed that the range of temperature from surface to 
bottom amounted to 9°-5, and that the fall of temperature between the 
depths of 10 and 15 feet amounted to 6°*2. 
Lochan na Lairige (see Plate XXVII.). — Lochan na Lairige lies 
to the west of Ben Lawers and flows into Loch Tay by the Allt a’ 
Mhoirneas, which enters the loch nearly opposite the entrance of the 
