98 
BATHYMETRICAL SURVEY OF 
prominent points. It flows northward by the An Lochain into the river 
Tilt, which also receives the waters from Loch Tilt at the head of the 
glen. It trends almost due north and south, and is a long narrow loch, 
or rather two lochs, there being a very narrow constriction near the 
middle dividing it into two portions ; the two lochs were quite distinct 
on the date of the survey, with a difference in level of about half a foot. 
It is about IJ miles in length, the southern portion being half a mile, 
and the northern portion three-quarters of a mile in length, and about 
one-sixth of a mile in maximum breadth, the mean breadth being about 
one-tenth of a mile, or 8 per cent, of the length. Its waters cover an 
area of about 81 acres, or one-eighth of a square mile, and it drains an 
area of about square miles, an area nineteen times greater than that 
of the loch. One hundred soundings were taken, the maximum depth 
observed being 81 feet. The volume of water contained in the loch is 
estimated at 103,197,000 cubic feet, and the mean depth at over 29 feet, 
or 36 per cent, of the maximum depth. The length of the loch is 80 
times the maximum depth and 222 times the mean depth. Loch Loch 
is peculiar in outline and in conformation. Besides the principal central 
constriction, which cuts the loch into two approximate halves, there 
are three minor constrictions, each accompanied by a shoaling of the 
bottom ; the most important of these divides the southern half of the 
loch into two basins, the more southerly of which has a maximum 
depth of 40 feet, while the maximum depth in the second basin is 53 
feet. But the greatest depth of the loch is found in the northern half, 
about one-fifth of a mile above the central constriction, where the loch 
is widest. Here the maximum depth of the loch (81 feet) occurs, 
approximately centrally placed, but rather nearer the western than the 
eastern shore, and here the slope of the bottom is very steep, a sounding 
of 80 feet having been taken about 200 feet off the western shore, giving 
a gradient of 1 in 2J, while a sounding of 75 feet was taken about the 
same distance off the eastern shore. From the position of maximum 
depth the water shoals, and the loch narrows, gradually towards the 
northern end. The area of the lake-floor covered by less than 25 feet 
of water is about 45 acres, or 55 per cent, of the total area of the loch ; 
that covered by water between 25 and 50 feet in depth is about 21 
acres, or 26 per cent. ; that covered by water between 50 and 75 feet in 
depth is about 10 acres, or 13 per cent., and that covered by more than 
75 feet of water is about 5 acres, or 6 per cent, of the entire area of the 
loch. Loch Loch was surveyed on July 9, 1903, but the elevation above 
the sea could not be determined from bench-mark ; from a spot-level of 
1480 feet a short distance up the inflowing burn, the elevation is 
probably about 1450 feet. There was no evidence that the loch rises 
more than a foot higher than on the date surveyed. 
T emperature Observations . — Serial temperatures were taken in the 
two halves of the loch : (1) in 40 feet of water near the southern end 
