100 BATHYMETRICAL SURVEY OF 



feet from the eastern shore. The last sounding indicates a very steep 

 slope in this position, equal to 1 in 1-9, and off the western shore further 

 north a similar steep gradient is indicated by a sounding of 36 feet 

 taken about 100 feet from the shore, equal to 1 in 2-8. The soundings 

 reveal, further, an ill-defined shallow ridge, running in a north and 

 south direction across the wide portion of the loch, covered by less than 

 30 feet of water, with deeper water on both sides. The area of the lake- 

 floor covered by less than 25 feet of water is about 23 acres, or 64 per 

 cent, of the entire area of the loch. Loch nan Eun was surveyed on 

 July 2, 1903 ; its elevation above the sea could not be determined from 

 bench-mark, but, estimated from spot-levels, its elevation must be about 

 2575 feet. There is evidently very little variation in the level of the 

 surface of the water, since no drift-mark indicating a higher level could 

 be seen, and a fall of a few inches would cease to feed the outflowing 

 burn, which forms a waterfall a few yards from the loch, the top of the 

 fall being at nearly the same level as the loch. 



Temperature Observations. The temperature of the surface water on 

 commencing the survey at 10.30 a.m. was 50 0< 0, and a series of tem- 

 peratures taken at noon in the deepest part of the loch gave the 

 following results : 



Surface 50'8 Fahr. 



25 feet 50'5 ,, 



45 49'8 



Lochs Craiglush, Lowes, Butterstone, Clunie, Drumellie, Rae, 

 Fingask, White, Black, and the Stormont lochs form a connected series 

 of lochs all draining into the Lunan burn, which flows into the river 

 Isla shortly before its junction with the river Tay; they all contain 

 pike and perch, and trout also are taken in Lochs Craiglush, Lowes, and 

 Drumellie. The group nearest the source of the Lunan burn consists 

 of Lochs Craiglush, Lowes, and Butterstone. 



Loch of Craiglush (see Plate XXIX.). The Loch of Craiglush is 

 situated in Drumbuie wood near Dunkeld, and is almost surrounded by 

 trees. Its shores are weedy, and where the Lunan burn enters there is 

 a large grassy flat formed of material brought down by the stream. It 

 trends in a north-east and south-west direction, and is over half a mile 

 in length, with a maximum breadth of over a quarter of a mile, the 

 mean breadth being nearly one-fifth of a mile, or 32 per cent, of the 

 length. Its waters cover an area of about 70 acres, or over one-tenth 

 of a square mile, and it drains an area of about 5| square miles an 

 area 52 times greater than the area of the loch. Over 50 soundings were 

 taken, the maximum depth observed being 44 feet. The volume of 

 water contained in the loch is estimated at 49,079,000 cubic feet, and 

 the mean depth at 16 feet, or 37 per cent, of the maximum depth. The 



