78 



Proceedings and List of Papers read. 



The optical properties are next considered, and the amount of 

 refraction produced by free atoms and molecules calculated. The calcula- 

 tions on the free atoms are of interest, inasmuch as it is shown that 

 they accelerate the velocity with which waves are transmitted. With 

 regard to the molecules, it is shown that the optical control may be 

 regarded as due to w 2 , the mean value of w 2 for the molecules, where w 

 is the angular velocity of rotation of the two atoms about their 

 common C.G. Dispersion is also accounted for, and depends essentially 

 on the distribution law of velocities. The effects of radiation from the 

 molecules are also considered in the course of the work. 



The rate of rotation of the plane of polarisation in a magnetic field is also 

 calculated, and the sign of the rotation shown to depend on which 

 atom has the larger mass. If the masses are equal no rotation is pro- 

 duced. The work borders in some ways with Professor W. Voigt's 

 investigations. 



The formulae obtained are applied to the case of oxygen to obtain 

 estimates of e/m 1 and e/m 2 , e being the charge and mi and m 2 the masses 

 of the two atoms. An estimate of w, and hence of 2r , the sum of the 

 radii of the two atoms, is also obtained. The value of e\m\ agrees closely 

 numerically with this ratio obtained from electrolytic considerations, while the 

 value of e/m 2 agrees closely with the value obtained from considerations of the 

 Zeeman effect. 



February 21, 1901. 



Sir WILLIAM HUGGINS, K.C.B., D.C.L., President, followed by 

 The LOED LISTER, F.R.C.S., D.C.L., Vice-President, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : — 



I. "An Attempt to Estimate the Vitality of Seeds by an Electrical 

 Method." By Dr. A. D. Waller, F.R.S. 



II. " On a New Manometer, and on the Law of the Pressure of Gases 

 between 1*5 and 0*01 Millimetres of Mercury." By Lord 

 Rayleigh, F.R.S. 



III. "An Investigation of the Spectra of Flames resulting from 

 Operations in the Open s hearth and ' Basic ' Bessemer Pro- 

 cesses." By Professor W. N. Hartley, F.R.S., and Hugh 

 Ram age. 



