280 



UPPER AIR OBSERVATIONS. 



Taking the mean temperature at sea-level as — 11'0°C. during the three ascents and applying 

 to this tempsrature the mean gradients, we obtain the following as the mean temperature at 

 the different heights throughout the dav : — 



Table 142. 



November 19. 1911. 



From the figures in table 141, it will be seen that from 500 to 2,000 metres the tem- 

 perature remained practically the same from 11 hours 30 minutes until 16 hours 30 minutes. 



Above this height the temperature changed in the course of the day by about two 

 degrees, the later ascent showing the higher temperature. 



It will also be noticed that at about 2,250 metres a different layer of air was met 

 with, for at about this height there is a distinct change in the gradient. The change in the 

 gradient was most marked during the morning ascent, the gradient being more uniform through- 

 out at the afternoon ascent. Thus the gradient from 500 metres to 2,000 was in the three 

 ascents, '69°, "65° and '67° C. per 100 metres respectively, while the gradient from 2,500 to 

 3,500 metres was -26° at the first ascent and '31° at the third ascent. 



The first and third ascents again reveal a region of the atmosphere in which the gradient 

 is less than in the regions above and below, and no doubt the same would have been found 

 to hold if the second ascent had gone high enough. On the mean of the three ascents we 

 have the following gradients : — 



Table 143. 



Mean gradient on November 19, 1911. 



The weather preceding the ascent was as follows : On the 17th a southerly blizzard had 

 existed, which, as was usually the case in the summer, was cold, the mean temperature 



