THE FRESH- WATER LOCHS OF SCOTLAND. 109 



Surface 59OFahr. 



10 feet 58-0 



2<) ,, 52-5 



30 50-2 



This series shows a range of 8'8 in the temperature of the water from 

 surface to bottom, there being a fall of 5*5 between 10 and 20 feet. 

 Compared with the temperatures taken in Fingask Loch on the same 

 day, this series indicates that the temperature of the upper layers of 

 water was comparable in both lochs, but at 20 feet the temperature was 

 nearly 3 lower than at that depth in the larger loch, the position of 

 the great fall in the temperature being nearer the surface in the smaller 

 loch. 



Black Loch (see Plate XXX.). The Black Loch lies immediately 

 to the east of the White Loch, the main road from Perth to Blairgowrie 

 passing between them. Neither inflow nor outflow was observed, but 

 if the water were to rise 6 or 8 feet it might overflow by the channel 

 under the road into the White Loch. It is almost surrounded by woods, 

 and the shores are weedy. It is over a quarter of a mile in length, 

 nearly one-tenth of a mile in maximum breadth, and its waters cover 

 an area of about 8 acres. Nearly 30 soundings were taken, and the 

 maximum depth observed was 7 feet. The voluma of water is estimated 

 at 1,611,000 cubic feet, and the mean depth at 4| feet, or 68 per cent, 

 of the maximum depth. The loch is almost of uniform depth, only 

 three of the soundings being under 5 feet, and these were near the east 

 end, so that the great body of water is from 5 to 6 feet in depth, the 

 area of the lake-floor covered by more than 5 feet of water being about 

 5 acres, or 64 per cent, of the total area of the loch. It was surveyed 

 on June 23, 1903, by means of a portable boat lent by Mr. Anderson, 

 carried over from Druidsmere, and the elevation above the sea was 

 determined, by levelling from bench-mark, as being 162-8 feet. 



Temperature Observations. The temperature of the surface water 

 in the main body of the loch was 60'l, while in the eastern portion it 

 was 59'0. The water in the eastern basin was clearer as well as colder, 

 as though there might be a spring there. Temperatures taken in the 

 deepest part of the loch gave the following results : 



Surface 60'l Fahr. 



3 feet ... 60-0 ,, 



4 59-8 



5 , 58'5 



6 57 c 'l 



showing a range of 3*0 throughout the 6 feet of water. 



To the south-west of the Black Loch lies Hare Myre, which was 

 visited on June 22, 1903, but could not be sounded because no boat was 

 available. The keeper said it was all shallow, and that the oars when 



