Minchin — Reflection of Light by Colored Papers. 445 



Art. XLYII. — Reflection of Light by Colored Papers ; by 

 Howard D. Minchin. 



Although the subject of reflection of light by various sur- 

 faces has received much attention, the question of the reflect- 

 ing power of colored papers and of wall papers in particular 

 seems to have attracted little notice. The importance of the 

 subject from an economic as well as from an artistic stand- 

 point would seem to justify the attempt to settle certain 

 features in the question even though the treatment be little 

 more than qualitative. 



The investigation is complicated at the outset by our inabil- 

 ity to specify definitely the exact sample of paper under exami- 

 nation as well as by our inability to reproduce such sample for 

 purposes of subsequent comparison and measurement. Never- 

 theless it has been thought worth while to submit the result of 

 a series of measurements upon the reflective powers of a set of 

 ordinary commercial papers. 



Under the head of metallic reflection the classic investiga- 

 tion of Hagen and Rubens,*- Langley,f Nichols, J Jamin,§ 

 Quincke, || and Drude,^[ are of the first importance. Wright,** 

 studied diffuse reflection of light on matt surfaces, while the 

 reflective powers of mercury and glass were investigated by 

 Walbott,tf and Walker,^ respectively. Investigations touch- 

 ing the reflection of light by colored papers are, so far as 

 known to the author, confined to the writings of Abney,§ 

 Abney and Festing,|j|| and of Kononowitsch,^!" but in none 

 of these can be found any mention of the subject under con- 

 sideration. 



Apparatus and Method. 



The measurements of the investigation here discussed were 

 made by means of a Brace spectrophotometer consisting of 

 two collimators T and T ; , a telescope A, and a Brace prism F 

 (fig. 1). The sources of light were two 220 volt 16 candle 

 power incandescent lamps. One was permanently fixed at 



* Hagen and Rubens, Ann. d. Physik., i, 352, 1900. 

 ■ f S. P. Langley, Phil. Mag., xxvii, 10, 1889. 

 iE. L. Nichols, Wied. Ann., lx, 401, 1897. 

 | J. Jamin, Ann. Chim. Phys. (3), xxii, 311, 1848. 

 || G. Quincke, Pogg. Ann. Jubelb'd., 336, 1874. 

 If P. Drude, Wied. Ann., xxxix, 481, 1890. 

 **H. R. Wright, Phil. Mag. (5), xlix, 199, 1900. 

 ffH. Walbott, Wied. Ann., lxviii, 471, 1899. 

 ££b. Walker, Wied. Ann., lii, 762, 1894. 

 §§ Abney, Roy. Soc. Proc, lxvii, 118, 1900. 

 If Abney and Festing, Phil. Trans., clxxii, 887, 1882. 

 THT Kononowitsch, Wied. Ann., lxvi, 317, 1897. 



