47o 



SMITHSONIAN' MISCELLANEOUS COLLECTIONS 



VOL. SI 



of the barometric formula of Koppen. Table 7 contains a collec- 

 tion of the associated values of temperature, pressure, altitude, and 

 temperature gradient for each two degrees of temperature for air 

 expanding adiabatically during the condensation stage. 



The initial pressure for all the cases of ascending air saturated 

 at temperatures 30 , 2 8°, 2 6° C, etc., has been assumed as 760 

 millimeters for an initial altitude of o meters or mean sea-level. 



In the general adiabatic equation and for temperatures above 

 o° C. or the rain stage, we have taken m = 3.60 corresponding to 

 an average quantity of moisture of 8 or 10 grams per kilogram of 

 dry air; but for temperatures below o° C, or in the snow stage we 

 have taken m = 3-44- The snow stage immediately adjoins the 

 rain stage, that is to say, the isotherm of the hail stage is not con- 

 sidered, therefore the table corresponds to the limiting case of 

 pseudo-adiabatic ascent in which all the water that is precipitated 

 separates from the ascending air. 



The difference of altitude has always been computed according 

 to the hypsometric formula of Koeppen for temperature intervals 

 of 2 from the respective pressures and average temperatures. The 

 total altitude of the ascension has then been computed by summa- 

 tion. The temperature gradient, or the diminution of temperature 

 per 100 meters has been computed for each condition from the 

 difference of altitude per 2 of diminution of temperature. 



Intermediate values can be taken from the table by interpola- 

 tion and we thus obtain, for example, the following small table H 

 for the temperature gradients per ico meters of altitude of satur- 

 ated ascending air. 



Table H 



For an adiabat whose initial temperature is t = io° the freez- 

 ing point occurs between the altitudes 1000 meters and 2000 meters, 

 This table H shows most plainly the slower rate of diminution of 



