( C5 ) 



Historical Account of Experiments regarding the Influence of 

 Colour on Heat, the Deposition of Dew, and Odours. By 

 James Stark, M. D. Edinburgh. Communicated by the 

 Author. 



Descartes was one of the first — if not the very first — of the 

 modern philosophers who turned their attention to the subject 

 of colour in connection with light and heat. It is not my inten- 

 tion to take any notice here of his theory of Hght. But in the 

 course of his investigations, he observed that a black colour 

 suffocates or extinguishes the rays which fall upon it, while 

 white on the contrary reflects them *. Kepler, as quoted by 

 Dr Priestley, had indeed previously asserted, that the reason why 

 black objects grow hot sooner than white ones, is not properly 

 owing to any difference in the colour, but because those sub- 

 stances which are black are of a more dry and inflammable na- 

 ture, -f- But his conclusion from the known fact was but little 

 calculated to promote the advancement of scientific inquiry. 



It remained for a philosopher of our own country, and one 

 to whom science is perhaps more indebted than to almost any 

 other individual of that age, for its subsequent progress, to 

 make the first correct experiments on the influence of colour 

 over heat. This was the Hon. Robert Boyle. His experi- 

 ments and observations upon colours were first published in the 

 year 1663, and form the basis of all that has since been written 

 on the subject. 



To try whether white bodies reflect light more than others, 

 he held a sheet of white paper in a sun-btam admitted into a 

 darkened room, and observed that it reflected a far greater 

 light than paper of any other colour. Green, red, and blue, 

 were then compared together ; the 7^ed gave much the strongest 

 reflection, the green and blue almost the same. The yellozv 

 compared with the two last, reflected somewhat more light. 

 Red and purple compared together, the former seemed to reflect 



* Dioptrics, p. 50. 



t Priestley's History of Discoveries relating to Vision, Light, and Colours, 

 p. 141. Lond. 1772. 



VOL. XVI F. NO. XXXIIl. .JULY 1834. E 



