380 Royal Society :— 



Heating-power of star 



> .xi-ottx-mj"^ 



(17-6) 

 = 0°'02l6 F. 

 For the observations <f> the scale was removed nearer the galvano- 

 meter, so that the effective radius for these readings was 2x17 

 inches against 2 X 37' 5 inches for the observations of the star. 



1869. August 11. 

 Observations of ilrcturus. 



0=27 div. 



^=114 div. 



c = 24 inches. 

 Effective radius for observations, 32 inches. 

 Heating-power of Arcturus 



-^xl-OtfxO-TMx »*f| 



= 0°-0180 F. 

 The mean result of the observations on these two nights is 



0°-0198 F. 

 as a measure of the heating-effect of Arcturus in raising the tem- 

 perature of the plate of antimony and bismuth when the heat is 

 condensed by the object-glass of 12*75 inches. 



If the absorption by the object-glass be considered insensible, the 

 direct effect upon the pile will be 



0°-000000685 F. 

 I have not yet determined the coefficient of absorption for the 

 object-glass ; but if it be provisionally taken at^, the direct heating- 

 effect of Arcturus 



= 0°-00000137 F. 

 The result may be otherwise stated as follows : — That the heat re- 

 ceived from Arcturus is sensibly the same as that from the whole face 

 of the cube containing boiling water at 400 yards. 



1869. August 14. 

 Observations of jS Lyrse at 8 h 38 m G.M.T. 

 0=15 div. 

 0=686 div. 

 Heating-power for /3 Lyrse 



10 -1-087X0725 x — =00039 F. 



(24) 2 " '686 



Observations were subsequently made ofaLyree ; but the zero was 

 unsteady, and as the night advanced clouds appeared and ultimately 

 interrupted the observations. 



1869. August 14. 

 a Lyra?. Star on a — star on (3 = 1 \ div. 



