86 BATHYMETRICAL SURVEY OF 



of the total area of the loch; that covered by water between 25 and 

 50 feet in depth is about 34 acres, or 29 per cent. ; while that covered by 

 over 50 feet of water is about 16 acres, or 14 per cent, of the entire area 

 of the loch. Loch Ordie was surveyed on June 3, 1903, and the level of 

 the surface of the water was determined by levelling from bench-mark 

 as being 946'3 feet above the sea. 



Temperature Observations. Serial temperatures taken in the deepest 

 part of the loch gave the following results : 



Surface 57'6 Fahr. 



10 feet 55'3 



15 ,, 49'5 



25 ,, 47'l 



50 45 7 



68 45-4 



The range of temperature from surface to bottom was 12 0> 2, there being 

 a fall of 5-8 between 10 and 15 feet. 



Loch na Craige (see Plate XXVI.). Loch na Craige (or na-Craig), 

 one of the best trout lochs in the district, is situated in Strathtay about 

 3 miles to the south-east of Aberfeldy, and flows into the river Bran by 

 the Cochill burn, which also receives the outflow from Loch Hoil. It is 

 surrounded by low, heather-clad hills covered with stony debris. It is 

 nearly half a mile in length, nearly one-eighth of a mile in maximum 

 breadth, the mean breadth being about one-twelfth of a mile, or 16 per 

 cent, of the length. The waters of the loch cover an area of about 24 

 acres, and it drains an area fourteen times greater, or more than half a 

 square mile. Nearly 30 soundings were taken, the maximum depth 

 observed being 13 feet. The volume of water is estimated at 7,871,000 

 cubic feet, and the mean depth at nearly 1\ feet, or 57 per cent, of the 

 maximum depth. The length of the loch is 195 times the maximum 

 depth, and 342 times the mean depth. Loch na Craige is a long, 

 narrow depression trending in a north- west and south-east direction, 

 or nearly north and south. It forms a simple basin, the deep water 

 running along the centre of the loch, the area covered by more than 10 

 feet of water being over one-third of a mile in length, but it is rather 

 curious to note that the maximum depth of 13 feet was found at the 

 extreme southern end of the 10-feet basin and comparatively very close 

 to the southern shore. The slope of the bottom is thus pretty steep 

 here, and in other places the slope is steep ; for instance, two soundings 

 of 11 feet were taken about 60 feet from shore, one off the western and 

 one off the eastern shore, giving a slope of 1 in 5 -5. About 63 per cent, 

 of the lake-floor, or about 15J acres, is covered by less than 10 feet of 

 water. Loch na Craige was surveyed on May 29, 1903; the elevation 

 of the surface of the water was determined by levelling from bench- 

 mark as being 1297-3 feet above the sea. 



