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 1 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 2 J 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 Jialves, 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. 



Temperature Observations. Serial temperatures were taken in the 

 two halves of the loch : (1) in 40 feet of water near the southern end 



