124 Chemical and Physical Notes 



of the thermometer was as good as could be desired, and, with the fresh 

 breeze blowing, it was thoroughly ventilated. I was again much struck 

 with the highness of the temperature of the air almost in actual contact 

 with the ice. The observations at i m. and 2 cm. from the ice were 

 repeated, giving substantially the same results at I m., dry bulb io'2, 

 wet, 5-i ; at 2 cm., dry bulb 6'8, and wet 3'2. The hot Fohn puffs were 

 more striking on the ice than on the land, owing to the greater difference 

 between their temperature and that of the surrounding air. At 4 p.m. 

 I left the ice and returned to the station of i o'clock on the hill-side, and 

 took the temperature at 4.35 p.m. dry bulb i6x>,> wet 8x>, relative 

 humidity 24-5. At the station in the valley below the glacier the 

 temperature was at 5.45 p.m., dry bulb i6'4, wet ii'8, and relative 

 humidity 56. These observations, besides showing the remarkable 

 conditions of the air over the glacier, indicate the fineness and warmth 

 of the weather which prevailed. 



"On the 2ist August another series of observations was made at the 

 stations on the land and on the ice. The breeze on the ice was not so 

 steady or so strong as on the igth, and about 5 o'clock in the afternoon 

 there was a heavy squall of rain and thunder. The same hot Fohn 

 puffs made themselves felt as before, without there being any means of 

 measuring their temperature. Their duration at their maximum tempera- 

 ture was never more than a few seconds, during which but little effect 

 was produced on the thermometer. It occurred to me that the only way 

 of gaining a knowledge of the temperature of these puffs of air would be 

 by comparing the rapidity with which the thermometer moved when 

 exposed to a known difference of temperature, with that observed in the 

 puffs. A number of observations was made with this view, by warming 

 the thermometer and noting its rate of cooling in air of known tempera- 

 ture. The reverse procedure was also followed on the ice. The thermo- 

 meter was cooled by being laid close to, but not touching, the ice, it was 

 then quickly raised to a height of I metre, and its rate of change of 

 temperature observed. In this way it was found that for an initial 

 difference of 4 the thermometer required 10 seconds to rise i; for 

 a difference of 3, 12 seconds; and for a difference of 2'5, 16 seconds. 

 These ratios were observed in the open air, and under the circumstances 

 where the hot puffs are observed. Unfortunately, owing to an accident 

 to the thermometer, very little use could be made of them. Where the 

 rate of change of temperature of the thermometer is used to determine 

 the temperature of the air, the movement of the air must be measured or 

 estimated. The observations made on the igth and 2ist August are 

 given in Table XXII. 



" For comparison with the temperatures on the ice on the igth, the 

 mean of the observations at the land station at 2.45 and 4.35 p.m. is 

 taken, and on the ice the mean of the observations at 3.20 and 3.55 p.m. 

 The altitudes of the two stations were as nearly as possible identical, and 



