10 



The Earl of Rosse on Lunar-Heat Radiation, [June 16, 



posed plate of glass, the second conclusion arrived at during the previous 

 season has been to a great extent confirmed. 



The following Table gives the values found for the percentage of the 

 moon's heat which passes through glass : — 



Date of 

 observation. 



Distance 01 

 moon from 



nnnn«if inn 



Altitude of 

 the moon. 



Percentage 

 of moon's heat 

 transmitted by- 

 glass. 







o 







r 15 



I3-3 



I. 



April 15th, 1870 



e 

 j 



j 2,0-k 



ICC 



II. 







I 24. 



1 6*6 



III. 







1 24 



14-5 

 14-6 



I. 

 II. 





3 1 



/ ' 

 \ 20 



IO'O 

 lO'Q 



I. 

 II. 





5° 



5° 



7*i 





February roth ... 



66 



44 



8-4 







77 



32 



9"3 







81 



I 44 

 1 16 



no 

 1 10 



I. 

 II. 



April 8th 



93 



3° 



I2 - 





March 8 th 



109 



27 



I3'p 





Mean =ir88. 



The same plate of glass which was used in I. and II. on April 15th, 

 and the experiments on the two following nights, was tested for the solar 

 rays, and the following values of the percentage of heat transmitted were 

 obtained : — 



April 15th 86-2 



86- 6 



April 1 8th 89-3 



84-3 



87- 1 



Mean on April 18th 86 8 



The piece of glass used on the other occasions, instead of being placed 

 at six or eight inches from the pile, was laid against the end of the pro- 

 tecting cone, or about half an inch from the face of the pile. When it 

 was placed in this position and tested for solar rays, an increase of devia- 

 tion in the proportion of 1*1 to 1 was obtained, owing to the "bottling up" 

 of the sun's rays as in an ordinary greenhouse, and the keeping off of 

 currents of air. 



It seems therefore to be clearly proved that there is a remarkable dif- 

 ference between the sun's and the moon's heat in regard to their power of 

 passing through glass. The amount transmitted varies from night to 

 night, and in the later observations the value was generally larger than in 

 the earlier ones. Possibly this may have arisen from the formation of a 



