50 Selim Lemsteöm. 



gins to exercise its influence, for evidently the condensation in the upper layers 

 of air near the surface of tlie eartli had begun earlier above the bog, and, 

 consequently, the radiation also. By this I do not mean to say that the mist 

 need be visible, for a great quantity of water, in the shape of iiifinitely small 

 drops, may occur in the air, vvithout disturbing its transparency to any note- 

 worthy degree. (lenerally this phenomenon is such as to make people say 

 that "the fog is rising", which, in most cases, is quite an incorrect way of 

 expression, for it is not the mist that rises, it is the cooling, which, in con- 

 séquence of radiation from the mist, rises higher and higher. 



Sufficiently cooled, the mist begins to fall, sinking, on its way, the tem- 

 peratiu-e of the surroundiug layer of air, and upon touching the plants on the 

 gronnd, it freezes to ice ot 0". By this process, the layer of air loses its 

 sheltering qualifies, and when ail the water, which, in conséquence ot the tem- 

 pérature and of pressure of moisture, must pass into a liquid state, lias fallen 

 down, an intense radiation begins, the destructive effect of which will now be- 

 come perceptible in the bog. It is evident, that the same process has taken 

 place above the meadow, but it began latei- and the quantity of the falling 

 over-cooled water was not so large as above the bog, in conséquence of which 

 the réfrigération in the layer of air had become less. 



c) Certain circumstances observed near springs in open meadow-ground, 

 will prove that the greater sensitiveness to frost of bog-lands is caused by this 

 phenomenon. It is a common say ing of the country people that „frost comes 

 from a cold springs", and indeed the action of night-frost genei'ally proves 

 greatest round them. 



In most cases, the spring is situated lower than the surrounding ground, 

 and during a frosty night, the cold aii- pours down to its surroundings, 

 thus effecting, in the vicinity of the spring, a more intensely cooled layer, 

 which circumstance in itself alone contributes to this sensitiveness to frost. But 

 springs do not always occupy the lowest situation and yet constantly remain 

 more sensitive than their surroundings! As the greater pressure of vapour, 

 which, in conséquence of evaporation near the spring, ouglit to exercise, after 

 the condensation, a sheltering influence against the radiation of beat from the 

 earth, how is this greater sensitiveness to frost to be explained? 



The condition of the layer of earth cannot exercise a noteworthy influence 

 hère, for even if, in the immédiate vicinity of the spring, it were somewhat 

 différent from the rest of its general character, this would not be enougli to 

 explain the above mentioned sensitiveness. 



We are of opinion that hère also a fall of over-cooled mist is the active 



