F. W. Very — Sky Radiation and Isothermal Layer. 379 



a deflection of +0*60 div. per degree F. The smaller deflec- 

 tion per degree of excess in this case is caused by the smaller 

 transmission of radiation from the hotter body whose maximum 

 of energy in the spectrum comes within the limits of the great 

 H band of aqueous vapor, while the radiation from bodies at 

 temperatures below the freezing point has its maximum in the 

 spectral energy-curve at a greater wave-length, and, conse- 

 quently, is less absorbed by the aqueous vapor of the atmos- 

 phere. Herein lies the explanation of the approximate 

 fulfillment of Newton's law of radiation within the range of 

 temperature included in these observations. In consequence 

 of these variations in the composition of the radiations to be 

 compared, the observations of these distant radiators at low 

 temperatures may be represented by a rectilinear proportion- 

 ality of 0*65 div. per degree F., neglecting the curvature which 

 would affect the representation of a radiation at higher tem- 

 perature or with greater absorption. 



Winter Measurements. 



Date. 



Time. 



1909 



State of the Sky. 



Jan. 20 



Jan. 21 



Jan. 29 



Feb. 1 



Feb. 2 

 Feb. 3 



4 p. 



5:38 p. 

 8:3?p. 



8:08 a. 



8:35 a. 



9:10 a. 

 11:41 a. 

 12:35 p. 



4:12 p. 



5:45 p. 



10:55 a. 

 11:50 a. 

 11:03 a. 

 10:40 p. 

 11:12 p. 

 11:25 p. 

 10:27 a. 

 9:21 a. 

 12:39 p. 



5:10 p. 

 7:38 p. 

 8:30 p. 



Fahrenheit temperature = 



Zenithal sky (milky bine) 



Overcast (deflection varying from — 24*4 

 to —38*6 as cloud became thinner and 

 stars faintly visible). _ 



Zenithal sky (deflection changing from 

 —400 to — 34*1 as blue sky turned to 

 thinnest cirro-stratus) 



Thin cirro-stratus ._ _ 



Cirro-stratus visibly thinner 



Good blue sky (milky blue) 



Faint filo-cirrus, slight mist 



(?) 'Too dark for cloud 



observations. Probably high cirrus 



Zenithal sky deep blue. A few cirri 



Feathery flocculent cirrus and cirro-stratus 



Zenithal sky deep blue. Quite clear .. 



" " clear 



! Thin cirro-stratus. Lunar halo 



Zenithal sky milky blue 



Zenithal sky a good blue _ 



Exceedingly faint cir-str. (scarcely more 



than a suspicion) _ 



Apparently clear _ 



Zenithal sky quite clear 





Ot3 



37-8 



0-79 



0-78 



50-40 



10-77 

 0-86 



0-76 

 '0 : 65 



§1 



a? o 

 H 



60 



« a 

 S.2 





•39-0 



■28- 



-36-1 

 ■23-6 

 -35-7 

 ■36-9 

 ■37-9 

 ■34-8 



■34-5 

 ■43-1 

 37-7 

 ■71-0 

 •47-0 

 ■30-8 

 ■28-5 

 •34-0 

 535 



-39-9 

 ■49-5 



■47-9 





+ 4-9 



+ 22-0 



+ 5-5 



+ 25-7 

 + 8-1 

 + 9-2 

 + 7-7 

 + 12-5 



+ 12-9 

 -10-3 



- 20 

 -56-2 

 -13-3 

 + 11-6 

 + 15-2 

 + 4-7 

 -22-3 



- 0-2 



- 0-4 

 -15-2 



- 12-7 



•15-1 



5-6 



-14-7 



- 3-5 

 -13-3 

 -12-7 

 -13-5 

 -10-8 



-10-6 

 -235 

 -189 

 -61-5 

 -25-2 

 -11-3 



- 93 

 -15-2 

 -30-2 



■17-9 



■18-0 

 ■26-2 



•24-8 



