320 



Prof. Frankland on some Winter 



[May 7, 



December 23rd. The sky was again deep blue and cloudless nearly 

 the whole of the day. The atmospheric pressure was 627*3 millims., and 

 the temperature eight minutes before sunrise, as shown by a black-glass- 

 bulb thermometer laid upon the snow, was again 18'3 C. ( 1 Fahr.). 

 The following therm ometric observations were made : 



I. Blackened bulb in vacuo. In sunshine. 



II. In the shade, the plain mercurial thermometer, with black glass 

 bulb, stood at -9-4 C. (15-1 Fahr.) at 11.30 A.M. It was freely sus- 

 pended in the air at a height of about three feet from the snow. 



At Greenwich the readings were, with blackened bulb in vacuo : 

 maximum 22-8 C. (73 Fahr.) ; at 9 A.M., 4-4 C. (40 Fahr.) ; at noon, 

 12- 6 C. (54-6 Fahr.); at 3 P.M., 22'8 C. (73 Fahr.). The maximum 

 in the shade was 8*3 0. (46 0< 9 Fahr.), and the minimum on grass in 

 the shade -2-3 C. (27'9 Fahr.). 



December 24th. As the Fluela pass, the highest carriage-road in Swit- 

 zerland, was still open for sledges, I determined to make some observa- 

 tions on the summit, which is 7890 feet above the sea, and consequently 

 about 2538 feet above Davos. Starting from Davos at 8 A.M., I arrived 

 at the summit of the pass, where there is a small hotel and telegraph 

 station, at 10.30 A.M. 



The early morning was somewhat cloudy, but, about ten o'clock, the 

 sky became perfectly clear and deep blue, and continued so until the sun 

 set behind the Schwarzhorn, a few minutes past noon. The following 

 temperatures were recorded : 



I. The blackened bulb in vacuo marked 41* 7 C. at 11 A.M. in the sun- 

 shine, 42-3 C. at 11.30 A.M., and 42'3 C. at 12 o'clock. 



II. The plain black glass bulb in the shade showed at noon 7'2 0. 

 when freely suspended about two feet above the snow in a brisk breeze. 



The highest temperature in sunshine which I have observed at Davos 

 at noon, with the blackened bulb in vacuo, was 42-5, which scarcely 

 differs from that read on the Fluela pass at the same hour. So far as 

 these limited observations go, therefore, they indicate that the solar rays 

 are not of appreciably higher thermal intensity at a height of 7890 feet 

 than at a height of 5350 feet. I may add that the thermometer in the 

 sunshine was sheltered from the wind on the Fluela pass, and was, in all 

 respects but one, in a more favourable position for attaining a high tem- 

 perature than at Davos. The one unfavourable condition was its expo- 

 sure to less solar heat reflected from the snow than at Davos. 



