1870.] 



Art /urns and a Lyra. 



1G3 



4. Without thermometers : 



Resistance R+1'437 13. A. unit. 

 From (1) and (4) R= 1-251 B.A. unit. 

 From (2) and (3) R,= 1-239 B.A. unit. 



The resistances are therefore each sensibly equal to 1*245 B.A, unit. 

 From (1) (2) and (3) (4) we find M-=105f>. 

 From the mean of sucli determinations I find 



I #r 1 087 - 



If, therefore, c is the distance of the pile from the cube in inches, 

 we have 



C= — x 1-087. 



C" 



And the heating-power of the star 



1 S0° f) 

 = i^Lxl'037xO-725x-. 



C (ft 



I may mention that the whole area of a face of the small pile may be 

 considered as effective in the focus of the equatoreal. 



The following observations have been made and reduced as above : — 



I860. Aug. 2. 

 Observations of Arcturus, altitude about 25°. 



0=23 dir. 



$=160 div. 



c = 1 7'G inches. 



Heating-power of star 



13 ^,X1-0S7X0725^^ 



(17*0)" 160V 

 = 0 C -021G F. 



a 



For the observations 9 the scale was removed nearer the galvanometer 

 so that the effective radius for these readings was 2 x 17 inches against 

 2x37*5 inches for the observations of the star. 



1869. August 11. 



Observations of Arcturus. 



0 = 27 div. 

 9=114 div. 

 c = 24 inches. 



Effective radius for observations, 32 inches. 

 Heating-power of Arcturus 



= 130., xl .08-xO; 2 5.X &x» 

 (24)- _ ' 114/0 



= 0°-0180 F. 



VOL. XTIII. N 



