26 



On the Injiuence of Color on Radiation. 



The results, with cyhnders Nos. 4 and 5, were few in number. 

 They are subjoined. 



The order from cylinder No. 4, is red, white, crimson, white, yel- 

 low ; the influence of the roughness of surface is here plainly shown, 

 by which the place of the white material, sulphate of baryta, is en- 

 tirely changed ; this is a quality difficult to appreciate, and yet here 

 we find it exceeding in influence any other property of the coating. 



A review of these results will show that we have been able to 

 establish, among the separate series, no order of color ; we have the 

 different orders as follows : 



A more satisfactory comparison, in respect to the number of sub- 

 stances employed, will be had by using the means, heretofore des- 

 cribed, for comparing together the results obtained with different 

 cylinders. For example, Nos. 1, 2, and 3, were each coated with 

 carbonate of lead, and through the numbers given by these coatings, 

 those found for the other coatings can be compared ; Nos. 1 and 4 

 were coated with vermilion, and Nos. 1 and 5 with gamboge. 



