THE FRESH- WATER LOCHS OF SCOTLAND. 103 



or one-sixth of a square mile, and it drains directly an area of over two- 

 thirds of a square mile, but since it receives the outflow from Lochs 

 Craiglush and Lowes, its total drainage area is about 8J square miles 

 an area 49 times greater than the area of the loch. Over 50 soundings 

 were taken, the maximum depth observed being 25 feet. The volume 

 of water contained in the loch is estimated at 53,238,000 cubic feet, 

 and the mean depth at 11| feet, or 45 per cent, of the maximum depth. 

 The length of the loch is 122 times the maximum depth and 271 times 

 the mean depth. The Loch of Butterstone forms a simple basin, the 

 maximum depth of 25 feet being observed approximately in the centre 

 of the loch, but nearer the western and southern shores. The deeper 

 water approaches much closer to the western than to the eastern shore, 

 off which the shallow water extends some distance into the loch, 

 especially opposite the point at the outflow, where the 10-feet contour- 

 line makes a great bend inward; this bend affects also the 20 -feet 

 contour-line, so that the 20-feet basin becomes somewhat crescent- 

 shaped. The area of the lake-floor covered by less than 10 feet of water 

 is about 52 J acres, or 48J per cent, of the entire area of the loch ; that 

 covered by water between 10 and 20 feet in depth is about 39J acres, or 

 36 \ per cent. ; and that covered by more than 20 feet of water is about 

 16 acres, or 15 per cent, of the total area of the loch. The Loch of 

 Butterstone was surveyed on June 1, 1903, and the surface of the water 

 was found by levelling from bench-mark to be 314'4 feet above sea-level. 

 The Ordnance Survey officers determined the level on July 31, 1899, as 

 being 314*8 feet above the sea. 



Temperature Observations. Temperature observations were taken 

 in the deepest part of the loch in the afternoon of June 1, 1903, with 

 the following results : 



Surface 63-0 Fahr. 



5 feet ... 62-8 



8 , 62-5 



10 , 57'0 



25 53 



This series shows a range from surface to bottom of 10, the greatest 

 fall being one of 5-5 between 8 and 10 feet. The water was warmer at 

 all depths than in Lochs Craiglush and Lowes at corresponding depths ; 

 the greatest decrease of temperature was observed at the same depth as 

 in Loch Craiglush ; the range of temperature was the same as that in 

 Loch Lowes, although there is only half the depth of water. 



Loch of Clunie (see Plate XXX.). The Loch of Cluuie lies in a well- 

 wooded valley, and is surrounded by cultivated ground, except at 

 Forneth woods. The castle on the island in the loch, which seems to be 

 artificial, is said to have been the birthplace of the Admirable Crichton. 

 On this island a pair of herons built their nest in 1903, but nest and 



