Atmospherical Phenomena. 257 



Baltic. The sea breeze, which blows in the morning, and al- 

 ways brings a moist air from the sea, is undoubtedly the cause 

 that the course of the absolute humidity should differ here 

 from what it is in the interior of Germany. We can under- 

 stand why, under these circumstances, the relative humidity at 

 the edce of the sea exhibits much less considerable oscillations 

 in the course of the day than it does at Halle. 



I have already mentioned the ascending stream of air by 

 whose action the amount of vapour at noon is less considerable, 

 notwithstanding the continued evaporation ; it follows from this, 

 that in the higher regions, the relations of absolute humidity 

 must be entirely different from those down below, for the di- 

 minution must be smaller from 10 o'clock a.m. until 3 p.m., it 

 must at a certain height disappear, and at length the maximum 

 of the amount of vapour must take place in the afternoon. A 

 series of observations which I carried on during the years 

 1832 and 1833 on the Alps, at the same time that similar ob- 

 servations were made at Bale, Bern, Geneva, and Zurich, con- 

 firmed what I have said in a striking degree, and at the same 

 time afforded a proof of the existence of the ascending current 

 of air, which, however, would also have been recognised by 

 means of the motion of the clouds. Thus, while down below, the 

 course was as I have given it for Halle, on the Rigi, 4000 feet 

 higher, the amount of vapour in the morning increased much 

 more rapidly than below, and this continued till noon ; this 

 was still more the case on the Faulhorn, at a height 6000 feet 

 above that of the low positions. 



If, with the fact above given, we further combine the cir- 

 cumstance, that the regular changes of the thermometer during 

 the day are much smaller above than below, it follows, that the 

 relative humidity above must exhibit an entirely different 

 course. The most humid and the dryest moments occur, at a 

 certain height, and also on plains, at sunrise and in the after- 

 noon ; but the difference between the indications of the hygro- 

 meter becomes smaller the higher we ascend, as is shewn by my 

 observations on the Rigi : we must, therefore, reach a point at 

 which the relative amount of moisture remains almost the same 

 during the whole day ; and higher up the dryest time occurs 

 in the morning, and the moistest in the afternoon. This in- 

 version of the relations observed below, is most satisfactorily 



