402 SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 



where To = 273°, corresponds to the zero-point of the Celsius scale. 

 Since, therefore, we can now introduce Celsius's degrees instead of abso- 

 lute temperatures, we find 



t=t'- 0.009932 . h, 



tberefore again the constant diminution of temperature of 1° C. for 

 every 100 meters, if we omit the consideration of the correction of the 

 density for variation of gravitation. 



2. 



Determination of the Diminution of Temperature in an Ascending Current 

 of Saturated 3Ioist Air ichich continually condenses a Portion of its 

 Ya^or. 



If, while the mass of air rises through the slight elevation dh, the 

 small quantity dq of vapor be condensed, then will the quantity of heat 

 r dq be liberated, if r represents the latent heat of aqueous vapor at the 

 prevailing temperature t. For moist air far removed from the point of 

 saturation, we have found the equation 



c' dt=—jdh, 

 in which 



jdh 



represents the equivalent of the quantity of heat which is abstracted 

 from the mass of air, and goes over into the work of expansion, whereby 

 the temperature sinks by dt degrees. 



This quantity of heat drawn from the mass of air will now only in 

 part affect it, since the liberated latent heat of condensation takes up 

 the other part. Therefore the equation must now stand 



c' dt ^ r dq = — j dh. 



From 



q = 0.623 - , 



there follows 



log q = log 0.623 + log e — log j), 



dq _ de dp 

 "q e p ^ 



whence 



, de dp 



and, by substitution in the original equation, 



c' dt 4- rq rq — 4- ^ dh = 0. 



■^ e ^ ly J 



.3ince row 



dp =1 — p dh, 



