THE FRESH- WATER LOCHS OF SCOTLAND. 251 
group of reservoirs, and Mr. Wm. LocLhart, o.e., of the Kirkcaldy and 
Dysart Waterworks for tracing of the new reservoir at HolL 
Gladhouse Reservoir (see Plate CVII.), the largest of the Forth 
reservoirs, lies at the base of the Moorfoot hills, about 13 miles south of 
Edinburgh. It is very irregular in outline, and 1 J miles in length from 
south-west to north-east, with a maximum breadth across the middle of 
nearly a mile. The superficial area is about 375 acres, or over half a 
square mile, and the drainage area about 12J square miles. The reservoir 
is, on the whole, comparatively shallow, 84 per cent, of the floor being 
covered by less than 25 feet of water, and only one sounding was taken 
in depths exceeding 50 feet, viz. the maximum of 55 feet near the sluice 
at the northern end. Here deep water approaches close to the shore in 
places, but the bottom is very uneven. The volume of water is estimated 
at 269 million cubic feet, and the mean depth at 16J feet. 
When surveyed on July 2, 1903, the elevation was 888‘6 feet above 
sea-level, and temperatures taken in the deepest part gave 60°’9 Fahr. at 
the surface, and identical readings of 58°’0 at depths of 30 and 45 feet. 
Rosebery Reservoir (see Plate CVIII.) lies about a mile to the north 
of Gladhouse reservoir, and is extremely irregular in outline. The main 
body trends north and south, and is two-thirds of a mile in length ; but 
its northern end sends off a branch in a south-easterly direction, so that a 
line drawn along the axis of maximum depth from end to end would be 
about a mile in length. The maximum breadth is less than a quarter of 
a mile, and the superficial area about 52 acres, whilst the area drained, 
including Gladhouse reservoir, is about 14 square miles. The maximum 
depth of 55 feet was recorded at the junction of the two arms of the 
reservoir near the outflow, where there is a small basin exceeding 50 feet 
in depth, equal to 11 per cent, of the total area, while 56 per cent, of the 
bottom is covered by less than 25 feet of water. The volume of water is 
estimated at 58 million cubic feet, and the mean depth at 25\ feet, which 
is much greater than the mean depth of Gladhouse reservoir, though the 
maximum depth is identical. 
When surveyed on June 30, 1903, the elevation was 731'5 feet above 
the sea. Temperatures taken in the deepest part showed a range from 
surface to bottom of 9"^*2 Fahr., and the decrease occurred mostly between 
30 and 35 feet, for within this interval of 5 feet of depth a fall of no less 
than 7J° was recorded — equal to a fall of 1^° per foot of depth ; while 
between 32 J and 35 feet a fall of 4J° was recorded — equal to a fall of 
nearly 2° per foot of depth. The readings were as follows : — 
Surface 
30 feet 
32 ^ „ 
35 „ 
40 „ 
50 „ 
57°-5 Fahr. 
57°-0 „ 
54°-0 „ 
49°-5 „ 
48°*5 „ 
48°-3 „ 
