THE FRESH-WATER LOCHS OF SCOTLAND. 251 



group of reservoirs, and Mr. Wm. Lockhart, O.E., of the Kirkcaldy and 

 Dysart Waterworks for tracing of the new reservoir at Holl. 



Gladhouse Reservoir (see Plate CVIL), 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 12 J 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. 



Eosebery Eeservoir (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 7 31 '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 7^~ was recorded equal to a fall of 1^ per foot of depth ; 'while 

 between 32 J and 35 feet a fall of 4^ was recorded equal to a fall of 

 nearly 2 per foot of depth. The readings were as follows : 



Surface 57'5 Fahr. 



30 feet 57'0 



32i >? 54 o. 



35 49-5 



40 48-5 



50 , 48-3 



