THE 

 LOiNDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE,. _ 



[FIFTH SERIES.] 



NOVEMBER 1896. 



XXXIX. Thermal Transpiration and Radiometer Motion, 

 By William Sutherland*. 



Part I. — Thermal Transpiration. 



THE comparative neglect into which the radiometer has 

 fallen is probably the natural compensation for the 

 exalted interest of its two or three years' reign over the 

 scientific imagination twenty years ago. In reading amongst 

 the papers about it published at that time, one gets an im- 

 pression of the laboratory of Crookes as of an arsenal where 

 night and day the equipment of a great expedition into the 

 unknown was being pushed on under the sleepless eye of a 

 patriot leader ; but in the answering bustle outside, Stokes, 

 Schuster. Stoney, Fitzgerald, Pringsheim, Reynolds, and 

 others soon showed that the new conquest was simply an 

 outlying part of the Kinetic Theory of Gases. Or, to vary 

 the figure, Crookes appears as a friendly counsel subjecting 

 Nature to a passionate and eloquent cross-examination with 

 his fellow physicists as judge and jury bringing in a verdict 

 for Kinetic Theory. And then the interest died away rapidly, 

 perhaps mostly on account of Reynolds's great paper " On cer- 

 tain Dimensional Properties of Matter in the Gaseous State n 

 (Phil. Trans, clxx.), which was probably held to settle the 

 essential points of general interest in radiometer motion as 

 consequences of the kinetic theory of gases, especially as the 

 same train of reasoning had led him to his discovery of 



* Communicated by the Author. 

 Phil. Mag. S. 5. Vol. 42. No. 258. Nov. 1896. 2 E 



