20 Sblim Lemström. 



roundings varies witli the height \ and the différence may, even in a small 

 inequality of height, amount to several degrees. In Pouillet's experiment t 

 was the average température of the surrounding air. Besides the fact that 

 justified objections may be made against the general acceptability of this me- 

 thod, we find that its application in the present case would soon present 

 almost insuperable difficulties and could not lead even to approximately corr- 

 ect results. 



If, in making the calculation, we hâve but a practical resuit in view, we 

 may get an important direction from the following explanation. 



Upon examining the two curves, PI. I, lo aud IIo, we shall find that 

 in the beginning, the température feil to a minimum, and, after rising slightly, 

 it remained almost constant for tlie rest of the night. 



From this we must draw the conclusion that the speed of réfrigération 



dt _ ES ^_ ES 



in which formula E — power of emission, dr = infinitely short time, 5"= the 

 surplus of température =T 6 and 6'= surface, P and G signifies weight 

 and sp. heat of the radiating body. 



From this it is seen that the radiation finishes when 



T^e = or T=d 



i. e. on June 11'' 1880 6= - 4",i and 

 on June 12'" = - 2'',5. 



With this we do not mean to affirm that 6 is constant ail the time, for 

 the condensations taking place in the atmosphère do not make this probable, 

 but the worth obtained may be used for an approximate calculation of the 

 radiated quantity of heat between two observed températures. 



Upon examining the variations in the rapidity of réfrigération in Curve 

 lo from 10 to 10 minutes, we shall arrive, when beginning from 9,5 p. m. 

 and considering the température to be constant during every interval and equal 

 to the average woith of the latter, at the following table: 



' In greater heights the tempex-ature decreases in proportion to the height un to 3,000 m, t'all- 

 ing 1» to every 150 m, but in the above-mentioned problem it is not a question of this decreasing, 

 but of finding out how much the température will rise within the first 200 m. 



