172 THE ANTARCTIC MANUAL, 
posed to any cold radiations from the ice. There is, therefore, no 
doubt that 6°°65 was the temperature of the air passing the bulb of 
the thermometer. The vertical distribution of temperature shown 
by these figures is remarkable. From a height of 1 m. to within 
2 cm. of the ice there is a gradient of 3°-4 per metre; in the 
remaining 2 cm. there is a gradient at the rate of 33° per metre; 
and, from various observations and considerations, it is probable that 
the moderate gradient is continued to within a millimetre of the ice, 
when it becomes precipitous. It is to be noted that the absolute 
humidity, as shown by the vapour tension of the air, has increased 
from 3-4 mm., at 1m. to 4°1mm.,, at 2cm.; showing that ice is 
being evaporated and transferred from the glacier to the atmosphere. 
The wind was blowing freshly down the glacier, and its velocity 
was measured by noting the time which pieces of paper allowed to 
drift took to reach the ice, and then pacing the distance. The mean 
velocity was found to be from 8 to 10 kiloms. per hour. 
“The observations made on the 21st and on the 22nd confirmed 
those of the 19th. The same variability of the air temperature at 
the land stations was noticed. Between 12.55 and 1.6 p.m. the 
following temperatures were observed by whirling :—16°°2, 16°:2, 
16°" 0, 15°*5,16"°O; 15°°5, 15°", 14°°2, 138. 14°, 13°, 18"+6, 
These are all good observations, and represent real variations of the 
temperature, or rather they indicate real variations of greater amount. 
Taking the mean of the last five observations, we have the tempera- 
ture of the air 14°°0, The wet bulb was found at 1.15 p.m. to be 
7°*5, giving a difference of 6°5. On the glacier the air felt closer 
than on the previous occasion. The temperature at 1 m. was 11°'5, 
and at 2 cm. from the ice 7°°3. The difference 4°°2 is less than on 
the previous occasion. The wind was much less strong, and yet the 
temperature close to the ice is higher. The wet bulb under the same 
circumstances, showed 4°°0. Five minutes later the dry bulb was 
observed at 1 m. 10°*2 and 9°-4, mean 9°°85. Another observation 
of the dry bulb at 2 em. from the ice gave 6°°6. The interval 
between the bulb and the ice was now reduced to the smallest 
possible distance, about 2 mm. The wind fell very light, and the 
thermometer remained at 8°-0, when the wind returned it fell to 
5°°8. The axis of the thermometer bulb would be about 5 mm. from 
the ice, and still the air is nearly 6° warmer than the ice. Another 
observation in the same conditions gave 5°5. The wet bulb was 
now exposed, but it had to be kept about 5 mm. off the ice; it 
showed 3°°2. At 2.43 p.m. a great volume of warm air came down, 
and the wet bulb ran up to 4°*5 in three or four seconds. With the 
