in the Air upon the Temperature of the Ground. 251 



described, those in ordinary type are interpolated from them 

 with the help of Pouillet's exponential formula. The table has 

 two headings, one which runs horizontally and represents the 

 quantity of aqueous vapour (W), and another that runs verti- 

 cally and represents the quantity of carbonic acid (K) in the 

 atmosphere. 



Table III. — The Transparency of a given Atmosphere for 

 Heat from a body of 15° C. 



-^ 



















1 



ico 2 . 



03. 



05. 



1-0: 



1-5. 



20. 



30. 



4-0. 



60. 



100. ! 



1 



37'2 



350 



30-1 



26-9 



23-9 



19-3 



16-0 



10-7 



89 



12 



34-7 



32-7 



28-6 



25-1 



22-2 



17-8 



14-7 



9-7 



8-0 



1-5 



315 



29-6 



25-9 



22-6 



19-9 



15-9 



130 



84- 



69 



2 



270 



25-3 



21-9 



19-1 



16-7 



131 



10-5 



6-6 



5-3 



2-5 



23-5 



220 



190 



166 



14-4 



11-0 



8-7 



5-3 



42 ! 



3 



20-1 



18-8 



16-3 



H'2 



12-3 



93 



7-4 



4-2 



3-3 



4 



15-8 



147 



127 



10-8 



93 



7-1 



5-6 



3-1 



20 



6 



10-9 



102 



8-7 



7-3 



6-3 



4-8 



37 



19 



0-93 



10 



6-6 



6-1 



5-2 



4-3 



3-5 



2-4 



1-8 



1-0 



0-26 



20 



2-9 



2o 



22 



1-8 



1-5 



1-0 



075 



0-39 



0-07 



40 



0-88 



0-81 



067 



0-56 



046 



0-32 



024 



0-12 



0-02 



Quite different from this dark heat is the behaviour of the 

 heat from the sun on passing through new parts of the earth's 

 atmosphere. The first parts of the atmosphere exert without 

 doubt a selective absorption of some ultra-red rays, but as 

 soon as these are extinguished the heat seems not to diminish 

 as it traverses new quantities of the gases under discussion. 

 This can easily be shown for aqueous vapour with the help of 

 Langley's actinonietric observations from Mountain Camp 

 and Lone Pine in Colorado*. These observations were 

 executed at Lone Pine from the 18th of August to the 6th of 

 September 1882 at 7 h 15 m and 7 h 45 m a.m., at ll h 45 m a.m. 

 and 12 h 15 m p.m., and at 4 h 15 m and 4 h 45 m p.m. At Mountain 

 Camp the observations were carried out from the 22nd to the 

 25th of August at the same times of the day, except that only 

 one observation was performed in the morning (at 8 h m ). 1 

 have divided these observations into two groups for each 

 station according to the humidity of the air. In the following- 

 little table are quoted, first the place of observation, and after 

 this under D the mean date of the observations (August 1882), 

 under W the quantity of water, under I the radiation observed 

 by means of the actinometer, under l x the second observation 

 of the same quantity. 



* Langley, ' Researches on Solar Heat/ pp. 94, 98, and 177. 



