134 Count Paul de Saint- Robert on a Barometrical Formula 



height corresponding to a decline of 1° is given by 



t — t =Ht +t); 



l l 



that is to say, by a quantity decreasing with the temperature t, 

 and therefore with the altitude. 



Seeing the incompatibility of the received formula with the 

 observed facts, it has appeared to me worth while to inquire to 

 what formula for computing heights from barometric observa- 

 tions Mr. Glaisher's results lead. In another paper I will en- 

 deavour to investigate the formula for atmospheric refraction 

 deducible from the same results. 



The decrease of temperature of the air from the earth to the 

 different elevations found by Mr. Glaisher, taking the mean of 

 his eight ascents, is shown in the following Table* : — 



; Height above the level of 

 the sea. 



Sky partially clear. 



Sky cloudy. 







Decrease of 



Average 



Decrease of 



Average 



From 



To 



temperature. 



height for a 

 decline of 1°. 



temperature. 



height for a 

 decline of 1°. 



feet. 



feet. 







feet. 



o 



feet. 







1,000 



72 



139 



4-5 



222 





2,000 



12-5 



160 



8-7 



230 





3,000 



171 



176 



12-8 



234 





4,000 



20-5 



195 



16-5 



242 





5,000 



23-2 



211 



19-6 



255 





6,000 



26-0 



230 









7,000 



28-8 



243 









8,000 



31-5 



254 









9,000 



341 



263 









10,000 



36-7 



272 









11,000 



393 



279 









12,000 



41-9 



286 









13,000 



44-4 



293 









14,000 



466 



300 









15,000 



487 



308 









16,000 



50-8 



314 









17,000 



527 



322 









18,000 



545 



330 









19,000 



56-3 



337 









20,000 



57-8 



346 









21,000 



591 



355 









22,000 



61-4 



358 









23,000 



62-4 



368 









24,000 



63-7 



377 









25,000 



64-8 



386 









26,000 



65-8 



396 









27,000 



66-8 



404 









28,000 



677 



413 









29,000 



68-5 



423 









30,000 



700 



428 







* It is perhaps not useless to anticipate an objection that may be made 

 against the manner in which these results were obtained. The heights con- 



