of Thermal Conductivity and Emissivity. 2#3 



found to be '95 ; assuming this as the ratio of k 2 to k u 

 we get 



- 2 = a/^? = 0-89, 



#1 V Lr, 



&i V Ictfi 



the mean result found by experiment being 0*85. 



It is to be noted that there is not so much difference 

 between the radii of the two rods as there was in the other 

 cases. 



Brass Rods, being the rods previously experimented on. 



.^ = 65 mm. ; 



#2 = 47*3 mm. (mean of three determinations). 



- 2 =-73, a/^ = -87. 

 # x V ri 



Copper Rods, previously used. 



x L = ()0 mm. ; 



t f 2 = 33 mm. (mean of three determinations). 



* 2 =-55, A /- 2 =-8G. 



Brass Rods. These are two new rods, which were used in 

 experiments to be described later. 



r 1 = 3*21 mm.. r 2 =l'69 mm., A /—— 73. 



V n 



As a mean result of a series of experiments, for # 2 = 5 cm., 

 x l was found to be 7*96 cm. ; or 



**=-63. 



Xi 



It must be pointed out, however, that with the Bunsen 

 burner the parts of the rod nearest the flame become visibly 

 oxidized, this being especially noticeable in the case of the 

 thicker rod — so much so that the increased emissivity so 

 obtained can apparently overcome the greater transmission of 

 heat of the thicker rod. Thus, with the above brass rods, 

 5 cm. on the thinner rod were found equivalent in this region 

 to 5*2 cm. on the thicker; and after the heating had con- 

 tinued for some time 3*7 cm. on the thicker rod balanced 

 5 cm. on the thinner one. The ratio given above, *63, is for 

 parts of the rods that were not oxidized, and did not become 

 so after several days' heating. 



