SUMMER ASCENTS. 



281 



when the blizzard was strongest being about -ig^'C. During the 18th the wind gradually 

 dropped and the temperature rose. The air became calm at 17 hours on the 18th, so that 

 a calm had existed for about 10 hours before the first ascent. 



Table 144. 



Record VIII. 



November 29, 1911. 



Time 12-30. Erebus smoke from N.W. 



The balloon ascended practically vertically moving first somewhat to the N.W. and then to 

 the S.E. The instrument fell about 2J kilometres to the south-east. At the time of the 

 ascent Erebus smoke was travelling from the N.W., so that the balloon entered the current 

 of air indicated by the movement of the smoke. There were a few cirrus clouds and during 

 the afternoon these thickened, and at 16 hours 7/lOths of the sky were covered with thick 

 cirrus or alto-cumulus clouds which showed fine iridescent colours. Over all the mountains 

 to the west there were heavy cumulus clouds and Erebus became obscured at about 14 hours 

 30 minutes. 



There had been very Uttle wind for the preceding forty hours, and during this time the 

 temperature had been fairly steady, varying only a degree or so on either side of — 8°C. 

 The temperature gradient was miusually high, the mean gradient in the first 2,500 metres 

 of the ascent being ■83°C. per 100 metres. Near to 2,500 metres the gradient became less, 

 and from this point the gradient decreased steadily until between 3,500 and 4,000 metres 

 it was only ■18°C. per 100 metres. At about 4,250 metres the gradient again became greater 

 and from 4,223 to 4,865 metres the temperature fell 3'7°C., this being a gradient of •50°C. 

 per 100 metres. 



In this ascent again the region of small gTadient is clearly shown with greater gradients 

 above and below, but the height at which it occurred was somewhat higher than on the 

 previous occasions. 



36 



