122 
BATHYMETRICAL SURVEY OF 
levelling, but was between 700 and 725 feet above the sea ; the water was said 
to be high, and might fall several feet. The loch supplies water to mills at 
Gatehouse by a tunnel made about 85 years ago through the hill to the 
west into High Creoch burn. Originally the outflow was to the east into 
the Tarff by a rocky channel, the overflow being over rock showing glacial 
stria 3 , and if the water were a foot higher than on the date of the survey, 
it would overflow on the east, and some of the water would reach the Tarff 
by the Glengap burn. The diameter from east to west is over half a mile, 
and from north to south rather less than half a mile, the superficial area 
being about 105 acres. The maximum depth of 33 feet was found towards 
the western shore. The volume of water is estimated at 56 million cubic 
feet, and the mean depth at 12 J feet. The 10-feet contour is continuous, 
and encloses an area equal to two-thirds of the entire lake-floor. There 
are two 20-feet areas, one towards the eastern shore, based on two 
soundings in 22 feet, separated by a shallowing with 15 feet on it from the 
deepest part of the loch lying to the west. The bottom is stony, no mud 
coming up in the sounding tube, and few weeds were noticed anywhere. 
From the table on p. 121 it will be seen that in the thirteen lochs under 
consideration 954 soundings were taken, and that the aggregate area of 
the water surface is about 4 square miles, so that the average number of 
soundings per square mile of surface is 238. The aggregate volume of 
water contained in the lochs is estimated at 1951 millions of cubic feet. 
The area drained by these lochs is nearly 299 square miles, or 73 times 
the area of the lochs. 
