On the Influence of Color on Radiation. 



25 



Cylinder No. 3. 



Nature of coating. 



Color. 



Carbonate of magne- 

 sia. 

 Carb. of lime, (chalk) 



Carb. of lead. 



Prussian blue. 

 Litmus. 



Bichromate potassa < 

 blue ) 



Alkanet. 

 Do. rendered 

 by potassa I 



India ink. 



do. 



Carb. of lead in oil of i 

 lavender. *_ 



Do. blackened by ^ 

 hydro sulphate of : 

 potassa. * 



Yellow- 

 ish white 

 White. 



White. 



Blue. 

 Blue. 

 Reddish 

 brown. 

 Crimson. 



Blue. 



Black. 



White. 

 Black. 



Oct. 11 



25 

 31 



Nov. 1 



11 



17 

 18 



21 



.S bj 

 > o 



S O 



o 



Sec.'s 



859.5 



879 



877 



805 

 831 



854 



926.7 



938.2 



776 



836 



843.5 



850 



a o 

 G bo 



862 



937 

 969 



894.5 



950 



819 

 869 



862 



See's 



Remarks. 



1011 

 1034 

 1032 



986 



C Rou^h, in specks 

 I projecting, 

 do. 

 Smooth and some- 

 what shining. 

 871jRough. 

 870 Not uniform. 



i Streaked and not 

 \ smooth. 

 989 Uniform. 



lOOlj 



959 Not smooth. 

 Q_^ i More uniform, 

 ^' , I (mean 697) 



Uniform, but not 

 glossy on surface. 



992 



1000' 



The effect of changing the crimson of alkanet to a blue was ap- 

 parently to decrease its radiating power about one per cent, or the 

 change of color in reality did not alter the power. The carbonate 

 of lead lost also slightly, or rather was not affected, by the change 

 not only of its surface, but of a considerable part of its mass, for the 

 oil of lavender having evaporated, the hydro sulphate of potassa pen- 

 etrated the coating. The substance by means of which the coating 

 was applied, seems not to have sensibly affected the radiating power; 

 the carbonate of lead applied with gum differing in radiating power 

 but four per cent, from that applied with oil of lavender. 



The colors rank from the foregoing table, blue, two varieties ; 

 black, brown, crimson, white, black, blue, white, three varieties. 

 There is no certainty that the litmus and alkanet, changed to blue 

 by potassa, were originally the same in color. The surfaces were 

 very different in regard to uniformity and smoothness ; the alkanet 

 was perfectly uniform, but not at all ghstening; it may be described 

 as of a uniform minute roughness. In this table, we have the greater 

 number of whites at the bottom of the scale of radiation, and of blue 

 and black at the top ; but this is all that can be said, for a white, a 

 black, a blue, are in close proximity near the middle of the scale. 



Vol. XXX.— No. 1. 4 



