4<M 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 51 



Since we shall make use of this formula therefore the value of the 

 barometric constant K t has been computed for each degree between 

 the temperatures + 30 and — 3 o°; these are given in table 2. In 

 continuation of the example already treated a tabular view of the 

 method of computation of the altitudes is given in detail in the 

 following table C: 



Table C 



The initial level of o meters altitude is here taken to be that at 

 which the temperature is 20 and the pressure 76o mm . 



Instead of determining the change of altitude for adiabatic 

 expansion from an initial to a final condition by applying the 

 barometric formula we may also combine the equation — dh = vdp 

 with the adiabatic equation / (p, t) and thus directly attain an 

 adiabatic hypsometric formula. This process has been applied by 

 Guldberg and Mohn as also by Hann following the precedent of 

 Peslin in order to deduce a formula for the diminution of tempera- 

 ture with altitude. 



The combination of the adiabatic thermal equation for dry aii 



= c p ' dT - A vdp 

 with the formula (14) gives the adiabatic hypsometric formula 



or the equation 



= c p ' d T + A dh 



-dh = Z*-dT = C dT 

 A 



(15) 



In this formula C = 100.7 meters or the change of altitude for a 

 diminution of i° Cand the vertical temperature gradient or the 

 diminution of temperature for 100 meters ascent is 0.993 C. 



