TEMPERATURE OF THE SURFACE OF THE MOON. 



29 



Photometric observations on moonlight. 



[Observer J. E. Kceler. All conditions favorable. The skj' "at first .slightly hazy, gradually becoming perfectly 

 clear." At the time (10 h. 30 ni.) the moon's hour angle was 1 h. 3 m. and her declination -f 10"^, corresponding to a 

 zenith distance of 34*^ and air-mass M=rl.21.] 



Color. 



Deep red 



Uright red 



Orange 



Yellow 



Green 



do 



Blue 



Bright violet 



Deep violet 



Reading of lamp-scale . 



Mean. 



12.0 

 10.5 

 7.9 

 8.9 

 5.9 

 12.0 

 8.6 

 6.5 



Kemarks. 



Wheel before lamp, index at3. 



Do. 



Do. 

 Wheel index at 5. 



Do. 

 No wheel. 



Do. 



Do. 



2.8 I No wheel: faint. 



These observations are reduced with the aid of the table of lamplight iuteusities on page 28. lu 

 the following table the last column contains the intensity of moonlight in different parts of the 

 spectrum, as compared with the standard lamp : 



In the observations of November 7 the sun was near the meridian (exact time not noted), and 

 his declination being — 16°, his zenith distance was about 50°, corresponding to an air-mass of 

 M=1.79. The condition of the apparatus was the same as in the previous measures. The sky was 

 a " fair hazy blue." 



Photometric observations on sunlight. 



Setting. Color. 



84 5'Deepred 12.2 



84 47 Bright red 9. 



85 40 Orange 15.4 



Sj 52 Yellow 13. 5 



87 8 Green 6.0 



87 42 Blue 8.9 



89 Bright violet 8.2 



89 Deep violet 6.0 



Reading of lamp-scale. 



Mean. 



11.7 

 8.6 

 1,5. 4 

 12. 5 

 6.2 

 9.5 

 8.3 

 5.6 



Remarks. 



Wheel before lamp, index at 5. 



Do. 

 No wheel. 



Do. 



Do. 

 Wheel before sun, index at 5. 



Do. 



Do. 



These observations are reduced in the .same way as those given in the tirst example. It is 

 evident that introducing the wheel photometer in the path of the sunlight increases the value of 



