-±04 Count Paul de Saint-Robert on the Measurement 



Table I. — Results of Mr. Glaisher's Observations upon the 

 Temperature and Hygrometric condition of the Air at every 



1000 feet of height. 



Height 



Partially clear sky. 



Overcast sky. 



calculated 

 by Laplace's i 

 iomiuicL* 







Decrease of Relative humi- 



Decrease of 



Relative humi- 





temperature, dity of the air. 



temperature. 



dity of the air. 



feet. 







o 









d f. 



63 



F. 



77 



1,000 



72 



68 



4-5 



77 



2,000 



125 



77 



87 



77 



3,000 



17-1 



76 



12-8 



80 



4,000 



20-5 



76 



16-5 



80 



5,000 



23-2 



69 



19-6 



83 



6,000 



260 



68 







7,000 



28-8 



64 







8,000 



31-5 



58 







9,000 



341 



52 



- 





10,000 



367 



52 







11,000 



39-3 



48 







12,000 



41-9 



48 







13,000 



44-4 



43 



* 





14,000 



466 



58 







15,000 



48-7 



53 







16,000 



50-8 



45 







17,000 



52-7 



33 







18,000 



54-5 



21 







19,000 



56-3 



36 







20,000 



57-8 



33 







21,000 



59-1 



32 







22,000 



61-4 



21 







23,000 



62-4 



16 







24,000 



63-7 









25,000 



64-8 









26,000 



65-8 









27,000 



66-8 









28,000 



677 









29,000 



68-5 









30,000 



70-0 







In order to avoid a vicious circle, we must put aside the heights 

 calculated by Laplace's formula grounded on a law of decrement 

 of heat inconsistent with that found by Mr. Glaisher, and we 

 must have the pressure corresponding to each temperature and 

 state of humidity. This is easily dqne by an inverse operation 

 from that employed by Mr. Glaisher to calculate the heights. 

 The altitude z being given, the pressure due thereto is found by 

 the formula 



log 



Po 



60159(1 + 



0+6' - 64? 

 900 , 



