TEMPERATURE OF SCOTTISH LAKES 
137 
7. One or two examples have been given of very low temperatures 
in lakes of moderate depth. Loch Shiel is of interest as an example of 
the converse. Observations taken on 9th July 1902 showed a tempera- 
ture of 45^-3 Fahr. at a depth of 400 feet, and of 56'' '5 at the surface. 
The length of Loch Shiel is over 17 miles, and the mean depth is 133 
feet, so that it is easy to understand this comparatively high temperature. 
8. Loch Dubh (nan Uamh basin) has a maximum depth of 153 
feet, but has a length of under half a mile, so that the ratio between 
depth and length is large— 1 to 15. This ratio is only equalled by 
the small loch on Eilean Subhainn in Loch Maree, in which no 
temperature observations were made. Observations in Loch Dubh on 
12th July 1902 showed a bottom temperature of 43° '5 Fahr. and a 
surface temperature of 59° '0, which contrast sharply with the observa- 
tions made in Loch Shiel a week earlier. 
9. After Loch Dubh, Loch Fender (Tay basin) is the loch with 
the largest ratio between depth and length. It is only one-third of 
a mile in length, but has a depth of 78 feet, the ratio being 1 to 22. 
Observations made on 5th June 1903 showed a surface temperature of 
58° '0 Fahr. and a bottom temperature of only 42° •4. The difference 
between the bottom temperatures of I^och Dubh and of Loch Fender 
is easily accounted for by the difference in the date of the observations. 
10. A contrast is afforded by Lochs Assynt (Inver basin) and 
Lurgain (Garvie basin), in which observations were made on 16th and 
9th September 1902 respectively. Loch Assynt is about 6 J miles long, 
has a maximum depth of 282 feet, and a mean depth of 101 feet. 
Loch liUrgain is under 4 miles long, and has a maximum depth of 156 
feet and a mean depth of 61 feet. The latter loch is crescent-shaped, 
so that the force of the wind must be somewhat broken in blowing 
along its surface. The axis of Loch Assynt, on the other hand, is 
nearly straight, and the lake has the reputation of being very stormy. 
This must account for the fact that in Loch Assynt the surface 
temperature was 53°*7 Fahr. and the bottom temperature 52° '0 — a 
range of 1°*7; while in the smaller and shallower Loch Lurgain the 
bottom temperature was 50° "3 and the surface temperature 56°*1 — 
a range of 5° "8. 
11. In Loch Achilty (Conon basin) observations are available in 
consecutive years. The loch is 119 feet deep, and only 1500 yards 
long — a ratio of 1 to 39, so that a low bottom temperature was to 
be expected : but the range of temperature observed is very large. 
Observations made on 11th August 1901 showed a temperature at the 
surface of 63°-5 Fahr., and at 70 feet 42°-3 Fahr.— a range of 21°-2 ; and 
on 23rd August 1901 a temperature at the surface of 61°"9 Fahr., at 
30 feet 52°-0, and at 60 feet 42°-8— a range of 19°-1. On 21st August 
1902 the surface temperature was 58° '4 Fahr., and the temperature 
