THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



APRIL 1864. 



XLIII. On the Condensation of Vapours on the Surfaces of Solid 

 Bodies. By G. Magnus*. 



[With a Plate.] 



ON a former occasionf I made the observation that a thermal 

 pile is raised in temperature when moist air of the same 

 temperature with itself comes in contact with it, and that it is 

 cooled when dry air of the same temperature passes over it. 

 This appearance can only be explained, so far as I can see, on 

 the supposition that the surface of the pile condenses watery 

 vapour from the atmosphere and is warmed by the latent heat 

 which is set free, and that the dry air takes water back again 

 from the surface of the pile, whereby the latter is cooled. The 

 pile displayed these effects not only when it was coated with 

 pine-soot or lampblack, but also when its surface was, as far as 

 possible, freed from such coatings, and quite metallic. That 

 powdery substances condense vapour of water and also gases is 

 known, and Jamin and Bertrand J have sought to measure this 

 condensation. I have myself§ also proved the condensation of 

 sulphurous acid on the surface of glass; but that a metallic sur- 

 face should absorb aqueous vapours in such quantity as to occa- 

 sion an appreciable elevation of temperature was very astonishing; 

 and it seemed to me to be well worth while to investigate this 

 absorption more closely. 



* Translated by Prof. Wanklyn from PoggendorfPs Annalen, vol. cxxi. 

 part 1 (1864, No. 1), p. 186. 



f Pogg.ilnn. vol. cxviii. p. 575 ; Phil. Mag. S. 4. vol. xxvi. p. 21. 



X Comptes Rendus, vol. xxxvi. p. 994. 



§ Poggendorff's Annalen, vol. lxxxix. p. 604. 

 Phil. Mag. S. 4. Vol. 27. No. 182. April 1864. R 



