16 On the Influence of Color on Radiation, 



Art. ITT. — Inquiry in relation to the alleged influence of Color 

 on the Radiation of non-luminous heat ; by A. D. Bache, Prof, 

 of Nat. Philos. and Chem., University of Pennsylvania. 



In the following essay I propose to submit a few remarks upon a 

 paper by Doct. Stark of Edinburgh, first published in the Transactions 

 of the Royal Society of London, for 1833, together with an experi- 

 mental inquiry into the alleged influence of color on the radiation 

 and absorption of non-luminous heat. 



The experiments were commenced soon after the paper referred 

 to, reached this country, and in them was adopted what seemed to me 

 the less exceptionable of two methods used by Doctor Stark, which 

 actually bear upon the question of the radiation of UOT-lurainous heat. 

 It was my intention to examine the matter more fully than had been 

 done by Dr. Stark, and to procure a more satisfactory induction by 

 experimenting on a considerable variety of substances. In this I had 

 the kind assistance of my colleague. Prof. Courtenay. 



While these experiments were in progress, the remarks of the Rev. 

 Professor Powell, of Oxford, on the paper of Doctor Stark, appear- 

 ed in the Edinburgh New Philosophical Journal. They confirmed 

 me entirely in the view of the inapplicability of most of the experi- 

 ments made by Dr. Stark, to the determination of the question of the 

 influence of color on the radiation or the absorption of heat. — Of 

 this class were the absorption of heat, radiant heat being understood, 

 as tested by the inverse of Count Rumford's method for comparing 

 the conducting powers of substances used for clothing ; also, as tested 

 by the effect of the heat from the flame of an argand gas burner, 

 thrown by a mirror upon the bulb of an air thermometer, which was 

 variously coated. Of the same class were the experiments on radia- 

 tion, as tested by the method used by Count Rumford, as above re- 

 ferred to ; the enveloping materials of the inner thermometer bein^ 

 wools of different colors, and colored wheaten paste. ' , 



Not included in this class are the methods of ascertaining the rate 

 of cooling of a thermometer of which the bulb was coated with differ- 

 ent pigments, and of a glass globe filled with warm water and vari- 

 ously coated. I gave the preference to a modification of this latter 

 method from the greater extent of radiating surface which may, with- 

 out inconvenience, be commanded by it. The glass globe used by 

 Dr. Stark, was one inch and a quarter in diameter; it was coated at 



