PAPEE BY PROF. BEZOLD. 239 



in its relations follows more or less closely the summer, while the night- 

 time is like the winter. 



Under the assumption of a prevailing- increase of heat the process pre- 

 sents itself somewhat as shown in the diagram (Fig-. 34) ; starting with 

 the condition a (in a cyclonic area) 

 the expansion with a diminution of g , jr 

 temperature proceeds according to 

 the curve a />, which descends rather 

 less steeply than does the the adia- 

 batic curve. Corresponding to this, 

 and also without reference to the 

 initial quantity of moisture, the dew- 

 point curve is first attained later, 

 that is to say, at a greater altitude 

 above the earth's surface than it 

 would be in adiabatic expansion. 



In the rain stage, therefore, the IG " ' 



curve of change of condition experiences a deflection toward the upper 

 side of the adiabatic, and therefore remains nearer the curve of satura- 

 tion. 



If now there occurs a still further greater addition of heat, as must 

 be the case during the period of insolation and at great altitudes, where 

 the condensation is less and the density of the clouds is correspond- 

 ingly diminished, then the air can again pass over into the dry stage 

 as is indicated in the portion c d of the curve. 



Thus the upper limit of the first layer of clouds theu would be at c. 

 At this limit, daring the summer days, more intense warming is in fact 

 to be expected, which through a further expansion, that is to say at a 

 greater altitude, on account of the diminished absorptive power of the 

 atmosphere, again passes over into the approximate adiabatic c d, by 

 which process, however, the dry stage is finally left and the snow stage 

 d e is entered. 



To this greater increase of heat at the upper limit of the clouds the 

 fact is certainly to be ascribed that the cirrus (or snow) clouds are not 

 directly continuous with the (lower or) water clouds, but generally 

 separated from them through a wide space such as corresponds to the 

 expansion from c to d. 



During the descent in the anti-cyclone or by reason of the compres- 

 sion the process must take place according to the curve e /, which in 

 general nearly agrees with the adiabatic of the dry stage. As we 

 approach the earth's surface however, on account of the strong absorp- 

 tion of heat occurring there, then and for that reason this curve can 

 depart to the right upwards from the adiabatic. This latter can how- 

 ever only occur temporarily, since in such a case we should have to do 

 with a condition, of unstable equilibrium. 



