PAPER BY PROF. BEZOLD, 



281 



These numbers, few as they are, still show that the layer of fog just 

 under its upper boundary was the coolest portion of the whole path 

 traversed by the balloon, and that close above this boundary the tem- 

 perature shows a rapid rise, but the relative humidity a rapid fall. 



Von Sigsfeld had obtained similar results even earlier, namely, Octo- 

 ber 5, 1887, on the occasion of an ascent of the Faulhorn, in Aargau, 

 for the purpose of takiug photographs. 



I give the appropriate data in the following table : 



* According to Trautwein ("Southern Bavaria, etc.," seventh edition, Augsburg, 1884.) the altitude 

 above the sea of Oberstdorf, which is that here adopted, is 808 metres; that of the summit of the Faul- 

 horn is 2,033 metres, so that the value 2,031 metres is an excellent testimony to the reliability of the 

 data. 



ti'he morning observation gave the altitude of Kiezlem as 1,058 metres, whereas the observation at 

 5 hours 10 minutes p. m. gave 1,078 metres, making use of the barometric pressure observed in the 

 morning in Oberstdorf. But if we assume, as is required by the observations at Augsburg and 

 Munich, that this reading had, during the intervening time, diminished by 1 millimetre, and further- 

 more adopt the very probable assumption that the aneroid could not perfectly foUow the rapid changes 

 of pressure during the descent, and therefore read about 2 millimetres too low, we shall obtain for 

 Riezlern the altitude 1,002 metres above the sea, or a figure that agrees almost perfectly with that do 

 duced from the morning observation. 



The numbers above tabulated were given on the one hand with a 

 well compared, quite reliable aneroid, and on the other so far as con- 

 cerns the temperatures with an Assmann's aspiration psychrometer of 

 the older construction. 



From the above table we see very clearly that the upper boundary 

 of the stratum of fog always shows a lower temperature than the neigh- 

 boring strata above and below. 



But whether this is as above assumed essentially the cold due to 

 evaporation can not properly be decided. The high relative humidity 



