On the Passage of Air through Capillary Tubes, 433 



of the imperceptibly thin film on the solid surface explains 

 the breath-figures obtained by Moser and Waidele with water 

 vapour, the photographic images (light-figures) of Daguerre 

 with mercury vapour, and the electric breath-figures of G. 

 Karsten and Bless with vapour of water, mercury, and iodine. 



Heidelberg, June 30, 1877. 



LIX. On the Influence of Temperature on the Passage of Air 

 through Capillary Tubes. By Francis Guthrie, LL.B* 



IN using " Marsh's " apparatus for testing for arsenic, it 

 may be noticed that, when heat is applied to the exit-tube 

 to decompose the arsenuretted hydrogen, the liquid rises in 

 the tube which supplies the sulphuric acid, thus leading to the 

 supposition that the passage of the gas through the exit-tube 

 is checked by the increase of temperature, thereby producing 

 increased pressure. This observation suggested the following 

 experiments on the effect of heat on the passage of gases 

 through capillary tubes. 



Fig. 1. 



The apparatus used was as follows: — From a vessel, A, 

 water drops into a funnel, b, causing a continued overflow. 

 The overflow falls into the concentric funnel B, and escapes by 

 the tube C. The middle of the funnel-tube is removable, and 

 may be replaced by tubes of any required lengths. The lower 



* Communicated to the Physical Society, April 13, 1878. A note of 

 the results was communicated to the British Association, 1876. 



Phil Mag. S. 5. Vol. 5. No. 33. June 1878, 2 F 



