368 
BATHYMETRICAL SURVEY OF 
feet ; this is nearly identical with the level determined by the Ordnance 
Survey officers on May 27, 1870, viz. 1268*6 feet. 
The bottom of Loch Ossian is very uneven, the transverse, as well 
as longitudinal, sections being undulate. Only the 25-feet contour 
follows the line of the shore. The 50-feet contour encloses an area 
2 miles in length. The south-western portion of this for three-quarters 
of a mile is exceedingly narrow. Near the middle of the loch it 
broadens to a quarter of a mile, and continues broad to near the out- 
flow. The area over 75 feet in depth is .fully a mile in length, that 
over 100 feet half a mile, and that over 125 feet a quarter of a mile in 
length. One mile from the upper end there is in the centre of the loch 
a shoal, over which the depth is only 11 feet. The approximate areas 
between the contour-lines, and the percentages to the total area of the 
loch, are as follows: — 
0 to 25 feet 
214 acres 
32 '6 per cent. 
25 ,, 50 „ 
234 „ 
35-6 
50 ,, 75 „ 
104 „ 
15*8 ,, 
75,, 100 „ 
72 „ 
10-9 
Over 100 ,, 
33 „ 
5T „ 
657 „ 
100-0 
It will be observed that the area of the lake-floor covered by water 
between 25 and 50 feet in depth is larger than the shore-zone covered 
by less than 25 feet of water. 
Tem'perature Observations . — The following temperatures taken at 
1 p.m. on May 16, 1902, show a range of less than 1° Fahr. : — 
Surface 
10 feet 
25 ,, 
50 „ 
100 „ 
44° -3 Fahr. 
44°T ,, 
43° -7 „ 
43° -8 „ 
43°*4 „ 
Loch Ghuilhinn (see Plate LXXXVII.). — Loch Ghuilbinn (or 
Gulbin) is a small and relatively broad loch, lying in the midst of the 
high mountainous region between Lochs Ericht, Treig, and Laggan. 
The long axis runs nearly north and south. The surrounding hills rise 
on all sides into peaks of well over 3000 feet. The loch is fully three- 
quarters of a mile long, and nearly half a mile in greatest breadth, 
with a mean breadth of a little over a quarter of a mile. The greatest 
depth is 49 feet, and the mean depth over 13 feet. The superficial area 
is about 146 acres, or nearly a quarter of a square mile, and the volume 
85 million cubic feet. It receives the drainage of a basin extending to 
29 square miles, including Loch Ossian. It is fed chiefly by the river 
Ossian, which, besides bringing the overflow of Loch Ossian, receives 
