244 PROCEEDINGS OF THE AMERICAN ACADEMY 



R Y G V 



61 100 121 735 



R V Slit. Distance. 



697 411 .100 mm. 1.5 m. 



735 411 .197 mm. 1.0 m. 



~38 



Total brilliancy, 362 c. p. Intrinsic, carbons, 3141. 

 Arc, 645. 



Moonlight. 



On account of interruption by clouds, the observations are not 

 quite so satisfactory as some of the preceding ones. Only one series 

 was made on the violet. The moon was just ten days old, and the 

 observations lasted from 9 to 10 p. m. Altitude, 44°. 



Mean Scale Readings. 



It would seem as if the last two yellows were too faint. They 

 were therefore discarded. 



It will be noticed that of all the violet rays sent out by the 

 sun, very few are reflected from the moon (see Fig. 1.), and that 

 the proportion of red rays is quite large, indicating that the surface 

 might partake somewhat of that color, — perhaps like brown lava. 

 And in this case its reddish appearance during total eclipse may not 

 be wholly, as heretofore supposed, due to the absorption of the blue 

 from the solar rays by our atmosphere. 



On account of clouds, the limits of the spectrum were not deter- 

 mined. 



