116 Mr. J. Y. Buchanan. On Rapid Variations of [May 31, 



they indicate real variations of greater amount. Taking the mean of 

 the last five observations, we have the temperature 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 occa- 

 sion. 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 cm. 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 ib 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 on 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 return of the breeze the wet bulb went back 

 to 3'0. The Fohn puffs were now very troublesome. At 2.52 P.M. 

 the wet bulb at 1 m. was 7'0 ; the dry bulb showed at 2.54 P.M., 

 11-0 ; at 2.55 P.M., 13'5 ; and at 2.57 P.M., 14-5. In one puff the 

 thermometer was observed to rise one degree in eight seconds, which 

 would make the true temperature of the air at the moment about 6'0 

 higher, or 19'5. 



At 3.30 P.M. I returned to the land stations, and again found the 

 same variable temperatures. Between 3.35 and 3.45 P.M. the tem- 

 perature varied between 16'0 and 13'5. The following averages- 

 were taken : 



3.45 P.M., dry, 14'3; wet, 8'0; relative humidity, 35. 

 4.0 14-0; 8-5; 42-5. 



Taking the first of these and the observations at 1 o'clock, we have 

 for the mean temperature of the air 14'15, and the wet bulb 7'75r 

 On the ice we have 



At 1 m., dry bulb, 9'85 ; wet, 5'6, and 

 At 2 cm., 7-3 ; 4'0. 



The difference in the temperature of the air at 1 m. is only 4'3, 

 and that between 1 m. and 2 cm. above the ice is only 2'55, while- 

 the air at 2 cm. is 7'3 warmer than the ice. 



On the 22nd August, the observations on the ice were repeated 

 with very much the same results. The temperature of the air 

 ranged from 9'0 to 9'5 at I m., and was 5 8/ 5 at 1 cm. from the ice. 



