February 14, 1919] 



SCIENCE 



157 



-CCr -55- -50- -45- -40' -35' -30" -25- -2Cr -15' -IC" -5' 0' 

 TEMPERATURE 



Fici. 1. Temperatures of the air at different elevations. 



ture gradient (rate of decrease of temperature 

 with elevation) of the free air is approxi- 

 mately that of a rising mass of saturated air; 

 and for the reasons (a) that frequently the air 

 is rising and saturated, and (b) that depar- 

 tures from the thus established saturation 

 curve develop but slowly, as explained, and art- 

 soon eliminated by its reestablishment. 



THE ISOTHERJfAL STATE OF THE UPl'ER AIR 



In April, 1S98, Teisserenc de Bort began at 

 Trappes, near Paris, a long series of frequent 

 atmospheric soundings with small balloons 

 carrying automatic registering apparatus. 



Among other things, he soon obtained tem- 

 perature records that indicated the existence 

 either of surprising errors in his apparatus, 

 or of wholly unsusjwcted conditions in the 

 upper atmosprere. The records generally 

 were tolerably satisfactory up to some 10 to 

 12 kilometers — satisfactory, because tlirough 

 at least the upper half of this region they 

 showed the temperature to decrease with ele- 

 vation at, very roughly, the adiabatic rate for 

 dry air. But somewhere in the neighborhood 

 of 11 kilometers elevation everything seemed 

 to go wrong, for from here on the records no 



