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. 
T em'perature 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 „ 
,, 47°-l „ 
50 „ 45°-7 ,, 
08 ,, 45° -4 „ 
The range of temperature from surface to bottom was 12°-2, there being 
a fall of 5°-8 between 10 and 15 feet. 
Loch na Craiye (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 7J 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 15^ 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. 
