THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



DECEMBER 1878. 



LIII. On the Mechanical Theory of Crookes's {or Polarization) 

 Stress in Gases. By G. Johnstone Stone y, M.A., F.R.S., 

 Sec. j Secretary to the Royal Dublin Society* . 



Introduction. 



npWO papers will be found in the first volume of the fifth 

 J- series of the Philosophical Magazine (March and April 

 1876), in which I endeavoured to explain the force that Mr. 

 Crookes had detected within vacuum-chambers, by pointing 

 out that when heat passes across the residual gas, the mole- 

 cules of the gas that tend respectively towards the heater and 

 towards the cooler must interpenetrate one another in a greater 

 degree than they would if the gas were in its ordinary or 

 unpolarized condition, and that this behaviour will render 

 the stresses within the gas unequal, causing the stress to be 

 greatest in the direction in which the augmented interpene- 

 tration takes place. 



When writing the foregoing papers, and afterwards when 

 writing a paper on the transfer of heat which accompanies 

 the phenomenon, I was under the mistaken impression that 

 the flow of heat between a heater and cooler in fixed positions, 

 and at constant temperatures, will become greater if the num- 

 ber of gaseous molecules that intervene is reduced below the 

 number required for the transfer of heat by the laws of " con- 



* From the ' Scientific Transactions of the Royal Dublin Society ' for 

 the year 1878. Read February 18, 1878. Communicated bv the Author. 

 Phil. May. S. 5. Vol. 6. No. 39. Dec. 1878. 2 D 



