268 Professor Kaemtz on the more important 



are all precipitated as rain, and the sky clears up, especially 

 when the barometer is slowly descending. The wind gradually 

 veers to E. and SE., the barometer sinks at the return of the 

 warm weather, and the sky becomes serene, while it still always 

 retains its pure colour. If the wind be weak, the sun acts with 

 power on the ground, and the ascending current of air carries 

 the vapours rapidly to the upper and cold strata of the atmo- 

 sphere, especially when the temperature of the day is quickly 

 rising. A saturation speedily ensues at different points, the 

 vapours are precipitated, and small rounded clouds {cumuli) 

 are formed, whose volume and number are increased until noon. 

 These clouds, a product of the ascending current of air, are con- 

 stantly driven higher, and consist entirely of fog-vesicles. 

 After the warmth has reached its maximum, the force of 

 the ascending current of air diminishes; the clouds sink 

 lower, and owing to their reaching warmer strata of air, at 

 length entirely disappear, so that at sunset the sky is quite se- 

 rene, and remains in this state until the following morning. 

 When the barometer falls slowly, and when the wind is east, 

 this succession of changes may be repeated for several days in 

 the same manner. But gradually the SW. makes its appear- 

 ance above, separate long-shaped cloudy fibres (cirri) shew 

 themselves in the sky, and the colour of the latter becomes duller 

 —at last almost milk-white. These clouds come for the most 

 part from directions w^hich lie somewhere between S. and W., 

 and their height must be very considerable, as is rendered evi- 

 dent by the circumstance that, even in the middle of summer, 

 they do not consist of fog-vesicles, but of flakes of snow, for we 

 find that the rays of light passing through them are as much re- 

 fracted as they would be by passing through the latter, and 

 hence give rise to lunar rainbows and mock-suns. Although the 

 measurements hitherto made are not sufficient to determine the 

 height of these clouds, which preceded by some hours or days 

 all the real hail-storms observed by me, yet, during a residence 

 of nearly a quarter of a year in the vicinity of the Jungfrau 

 and the FinsteraarJiorn, notwithstanding all the attention I 

 bestowed, I have never seen a single one of them lower than the 

 summits of these mountains. When the SW. blows for some 

 time above, the wind at the surface veers gradually to that 

 quarter, the barometer sinks, and, as at every moment new 



