114 
BATHYMETRICAL SURVEY OF 
depth. The length of the loch is 148 times the maximum depth and 402 
times the mean depth. Loch Freuchie forms on the whole a simple 
basin, but with a few minor undulations of the bottom. The 25 -feet 
basin is sinuous in outline, especially towards the south-east end, and is 
over IJ miles in length, approaching close to the north-west end, but 
distant less than a quarter of a mile from the south-east end. The 
50-feet basin, half a mile in length, is contained in the northern half of 
the loch, and nearer the eastern than the western shore, the maximum 
depth of 62 feet having been observed in two places, with soundings of 
60 feet between them. Cones of alluvium have been formed at the 
mouths of the Turrerich burns at the northern angle of the loch, and at 
the entrance of the Allt a’ Mhuilinn about midway along the western 
shore. The area of the lake-floor covered by less than 25 feet of water 
is about 225 acres, or 65 per cent, of the total area of the loch ; that 
covered by water between 25 and 50 feet in depth is about 95 acres, or 
27 per cent. ; and that covered by more than 50 feet of water is about 
28 acres, or 8 per cent, of the entire area of the loch. Loch Freuchie 
was surveyed on June 5, 1903, and the height of the surface of the 
water above the sea was determined, by levelling from bench-mark, as 
being 867’45 feet ; when levelled by the officers of the Ordnance Survey 
on August 17, 1899, the elevation was found to be 870-8 feet above 
sea-level. 
T eviperature Observations . — Temperature observations taken in the 
deepest part of the loch at 7 p.m. gave the following results ; — 
Surface 
10 feet 
15 ., 
25 ,, 
40 ,, 
58° -6 Fahr. 
58° -3 „ 
57° -6 ,, 
53° -0 „ 
50° -0 ,, 
(10 „ 
49° -4 
This series shows a range of temperature from surface to bottom of 
9°-2, there being a fall of 4°-6 between 15 and 25 feet, and a further 
fall of 3°-0 between 25 and 40 feet. 
Loch Hoil (see Plate XXXI.). — Loch Hoil (or Oyl, or Thuill) lies to 
the south of Aberfeldy, and flows by the Cochill burn into the river 
Bran. It contains trout, perch, grayling, and gudgeon. It is sur- 
rounded by low, rounded, hummocky, heather-clad hills. Its shores are 
stony; the bay leading to the outflow is very shallow and full of weeds. 
It is very irregular in outline, and over one-third of a mile in length 
from north-west to south-east, under one-third of a mile in maximum 
breadth from north-east to south-west, the mean breadth being one- 
seventh of a mile, or 43 per cent, of the length. Its waters cover an 
area of about 35 acres, and it drains an area six times greater — an area 
