ON THE ENERGY OF STORMS MARGULES 587 



for moist air. But in order that this be possible, we must add 

 heat during the overturning and the total quantity for the whole 

 mass will be (Q). Hence according to (6*) the available kinetic 

 energy will be 



d K + (R) = (Q) + C pa f(T- V) dm a + C pp j (T - V) dmp 



and the flow of heat is determined by the equation (F) 



L'dm (F*) 



(0)-J 



r 



It is to be noted that L'dm' r is not exactly the latent heat of 

 condensation that the element dm receives during its whole path, 

 but the quantity of heat evolved by the condensation of dm' r at 

 the temperature of the final stage of dm. This is in accordance 

 with the assumption that was made in the computation of I e where 

 it was assumed that condensed water is carried along with the air 

 to its final stage. 



We will therefore now investigate the influence of the latent heat 

 of condensation on the available kinetic energy, by means of 

 another system that is more perspicacious than moist air. Since 

 the local difference of composition is of slight influence in this 

 problem we will replace the moist air by a homogenous gas that 

 can expand with increase of heat. 



§(36) Equations for a fictitious gas that receives increase of heat 

 by its own expansion. 



The fictitious gas that we will introduce instead of moist air 

 behaves when it is compressed, like dry air and obeys in general the 

 equation of elasticity p = RTpi. But with every diminution of 

 pressure there is connected an addition of heat so that for expansion 



dT dp 



T- l T- • • - (1) 



where X differs from the k that holds good during compression. 

 The quantity of heat imparted by this law of expansion is 



RT dp 



dQ = C p dT - -ydp= - (R-XC v )Tj . . . (2) 



