VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 771 



Min. Sun. Black paper scattering. 

 Exper. 199- &H 66 This paper scatters 993 rayg of heat, 



5 70$ 68 ... 4} : 2 = .410. and 420 of light. 



From these experiments it seems to be evident, that in scattering heat, the 

 colour of the object is out of the question ; or, at least, that it is no otherwise 

 concerned than as far as it may influence the texture of the surface of bodies. For 

 here we find that pale-green, which is brighter, or scatters more light, than dark- 

 green, yet scatters less heat. Even black, so generally known to scatter but little 

 light, scatters much heat. But, in order to put this surmise to a fairer trial, I 

 made the following experiments with my new machine. 



Exper. 200. — I covered one of the tablets with white 

 paper, and the other with black. The quantity of Min. White paper. Black paper scattering, 

 sunshine admitted through the 2 openings, of l£ inch 7l| 72 



in diameter each, being equal, I found the heat scat- 5 75* 75 . . . 3$ : 3 == .774 



tered on both thermometers to be as follows. 

 I turned now the tablets, and had, 



Min. Black paper. White paper scattering. These results, agreeing suffi- 



73£ 72| ciently well together, show that 



5 r&f 75i ... 2-| 3-l = .760. if we make white paper our 



standard, and suppose it to scatter 1000 rays of heat, and 1000 of light, then will black paper scatter 



j67 rays of heat, and 420 of light. 



Min. White paper. Black muslin scattering. 

 Exper- 201. 73| 73$ This scatters 813 rays of heat ; 



5 77$ 77 ... 4:3j = .S13. and, when it is suspended so that 



the rays which pass through it may not be reflected, it scatters only 64 rays of light. 



Exper. 202. — As my intention at present was to find a black substance that should scatter more heat 

 than a white one, I thought it would be the readiest way to examine the white and black objects sepa- 

 rately, that of all the white ones I might afterwards Min. White paper. White linen scattering, 

 take that which scattered least, and compare it with 74| 75 



the black one which scattered most. 5 79 79\ • • • *£■ : 4 k = 1000 



These objects scatter heat equally, and very nearly also light ; for our table gives for linen 1008. 



Min. White paper. White cotton scattering. These objects scatter heat equally. 



Exper. 203. 74^ 74-f White cotton scatters 1054 rays 



5 78^ 78| . . . 3-£ : 3| = 1.000. of light. 



Min. White paper. White muslin scattering. 

 Exper. 204. 73% 73$ White muslin scatters 875 rays of 



5 77| 76i . . . 4 : 3\ = .875. heat, and 827 of light. 



Min. White paper. White Persian scattering. 

 Exper. 205. 74 § f4* White Persian scatters 1074 rays 



5 77i 78^... 3f : 34 = .1074. of heat ; and, when suspended 



like the black muslin in the 201st experiment, it scatters 67 1 ray6 of light. 



Min. White paper. White knit worsted ; rough side outwards. 

 Exper. 206. 51 51| White worsted scatters 1231 rays 



5 52-| 53f . . . H : 2 = 1.231. of heat, and 620 of light. 



White paper. White chamois leather : the smooth side exposed. 

 Exper. 207. 74$ 744 White chamois leather scatters 



78f 79 . . . 3| : 4f = I.167. 1 167 rays of heat, and 1228 of 



light. 



Black paper. Black velvet scattering. 



Exper. 208. 75$ 75% Making now black paper the 



79% 80 . . . 3^ : 4-L = 1.179. standard, and supposing it to 



scatter 1000 rays of heat, and the same of light, then black velvet scatters 1 179 rays of heat, and only 



17 of light. This last number we obtain, by dividing the tabular number 7 1 for black velvet, by 



.42 which is the proportion of black paper to white. 



Min. Black paper. Black muslin scattering. 

 Exper. 209. 75^ 75\ Black muslin scatters 11 92 rays 



5 78-f 791;." 3f • ii ss 1-392. of heat, and 43 of light, 



5 F2 



