1896 - 97 .] T. S. Muir on Observing Station on Ben Nevis . 285 
(4) At 21 h. on the same day it was 1°'7 higher; wind E., 
very light, and station between two fog-systems. 
On each of these occasions the difference from the base was con- 
siderably larger, though slightly below the mean. It will be 
noticed, that at each of those periods except the second, the station 
was in a kind of pond between two systems of fog, one of which 
belonged to the upper part of the mountain, with a loiver surface 
varying from 2300 to 2600 feet, and the other to the lower part of 
the mountain, with an upper surface varying from 2000 to 2350 
feet. In the second case there was mist at the station, and 
extending downwards, probably 400 feet. 
The temperature at the middle station was closest to that of the 
base — (1) At 21 h. on the 2nd, when it was 3°T lower; wind 
27.N.E., light, and a small passing cloud on Meall-an’t-Suidhe — - 
the hill overlooking the station — between the heights of 2000 and 
3000 feet. 
(2) At 21 h. on the 10th it was 3°”1 lower ; wind S., calm; no 
fog visible, and very clear. 
(3) At 10 li. on the 21st it was 3°9 lower ; wind E.S.E., calm; 
no fog visible ; bright sunshine at the station. During the night 
the minimum temperature was registered, and my thermometer 
gave a sudden leap from 3 6° *9 to 40”° 9, while the base temperature 
rose only 2° ‘9. Afterwards there was a break away, and at 15 h. 
the difference was as much as 10° "7. 
In the first of those cases there was only light passing fog about 
the level of the station, but half-a-mile away ; and in the other two 
there was no fog at all. 
It is worthy of notice that, while the summit was once warmer 
and twice within 2° of the intermediate, the latter was never 
warmer than the base, and never less than 3° colder at any observation. 
The greatest differences from the summit temperature occurred : 
(1) At 14 h. on the 13th when it was 13° ’7 higher. The wind 
was W., light ; there was bright sunshine, no fog visible, and it 
was the warmest day of the month. 
(2) At 18 li. on the 14th it was 11°‘9 higher. The wind was 
S.S.W., moderate to fresh — squally. There was fog about 600 
feet above, and passing at the lake about the level of the station, 
and thunder later in the evening. 
