( 249 ) 



Inquiry in relation to the alleged iiifluence of Colour on the 

 Radiation of Non-luminous Heat, By A. D. Bache, Pro- 

 fessor of Natural Philosophy and Chemistry, University of 

 Pennsylvania. * 



In the following essay I propose to submit a few remarks 

 on a paper by Dr Stark of Edinburgh, first published in the 

 Transactions of the Royal Society of London for 1833, to- 

 gether with an experimental inquiry into the alleged influence 

 of colour on the radiation and absorption of non-luminous heat. 



The experiments were commenced soon after the paper refer- 

 red to reached this country, and in them was adopted what 

 seemed to me the less exceptionable of two methods used by Dr 

 Stark, which actually bear upon the question of the radiation of 

 non-luminous 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, Professor Courtenay. 



While these experiments were in progress, the remarks of the 

 Rev. Professor Powell of Oxford on the paper of Dr Stark ap- 

 peared in the Edinburgh New Philosophical Journal. They 

 confirmed me entirely in the view of the inapplicability of most 

 of the experiments made by Dr Stark, to the determination of 

 the question of the influence of colour 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 sub- 

 stances used for clothing ; also, as tested by the effect of heat 

 from the Jlame of an Argand gas-burner, thrown by a mirrori , 

 upon the bulb of an air-thermometer which was variously coat- 

 ed. Of the same class were the experiments on radiation, as 

 tested by the method used by Count Rumford, as above referred 

 to, the enveloping materials of the inner thermometer being 

 wools of different colours, and coloured wheaten paste. i 



Not included in this class are the methods of ascertaining th^jf* 

 rate of cooling of a thermometer, of which the bulb was coated 



• Silliman's Journal of Science, vol. xxx. p. 16. 



