410 
Proceedings of the Eoyal Society 
land, so that its waters in winter are probably colder than those of 
the lake lower down. 
In accordance with the autumnal character of the distribution* 
the temperature of the first 10 fathoms approaches uniformity at 
all the stations. It is highest at Ardlui, being 56° *2, and lowest 
at Rowardennan, being 55° *1. The steepest gradients are all 
between 10 and 20 fathoms. They are steeper in the shallow 
basins than in the deep ones ; in the Ardlui basin the average 
gradient is l°-53 per fathom between 10 and 15 fathoms. 
On 7 th September the Inversnaid station was revisited, and the 
temperatures on the gradients accurately ascertained by sending- 
thermometers to every fathom, from 13 to 17 inclusive, with the 
following result : — 
Observations at Inversnaid, 7th September 1885. 
Depth. 
No. of Ther- 
mometers. 
Temperature 
degs. Fahr. 
Gradient, 
deg. per fathm. 1 
1 
13 
21 
52°0 
O 
14 
47 
51-25 
0*75 
15 
79 
49-8 
1-45 
16 
9 
48-8 
1-0 
17 
80 
47-25 
1-55 
The mean gradient in these four fathoms of water is 1°T9 per 
fathom, the maximum is 1°*55 between 16 and 17 fathoms. It 
is therefore probable that the actual maximum gradient in the Ard- 
lui basin may be as much as 2° per fathom. 
Owing to a mistake, 105 fathoms of line were paid out at Cul- 
ness and Inversnaid instead of 1 00, which accounts for the irregular 
intervals between the thermometers at the deeper depths. From 
30 to 70 fathoms the temperature of the water is slightly higher at 
Stuckgowan than at Inversnaid. From 70 fathoms to the bottom 
the water at the three deep stations is sensibly uniform, namely, 
41°-8. On 7th September the three thermometers, Nos. 47, 79, 
and 80, were sent down together to 60 fathoms at Inversnaid, and 
their corrected temperatures were 41°*9, 41°*9, and 41 0, 85. There 
is, ^therefore, a fall of 0T° between 60 and 100 fathoms at this 
season of the year. The same thermometers were also sent to 30 
fathoms in the Luss basin, and their corrected readings were 47°*0, 
47°-0, and 47°-0. 
