572 



SCIENCE 



[N. S. Vol. LIV. No. 1406. 



world to make a thorough and organized an- 

 thropological study of this interesting and 

 little-known group. 



H. E. G. 



LECTURES BY PROFESSOR LORENTZ AT THE 

 CALIFORNIA INSTITUTE OF TECHNOLOGY 



The following is the provisional outline of 

 the extended course of lectures on " Light 

 and matter " to be delivered by Professor 

 H. A. Lorentz, of Haarlem, Holland, during 

 the winter quarter at the California Institute 

 of Technology at Pasadena: 



Older theories of light. Maxwell's theory. Max- 

 well 's equations. 



Propagation of light in ponderable bodies. 



Huy gen's principle. 



Interference phenomena. Professor Michelson's 

 methods. 



Propagation in a dispersive medium. 



Group velocity. 



Which is the velocity that is determined by the 

 measurements ? 



Considerations on (special) relativity. 



Fresnel's coefficient. 



Momentum, energy and massi. 



General considerations on the constitution of elec- 

 trons, atoms and molecules. 



Models of the atom. Thomson, Rutherford, Bohr. 



Theory of quanta. 



Parson's electron. Lewis's and Langmuir's atom. 



Bohr 's theory. 



Principles of correspondence. 



Atoms in stationary states not radiating. 



Emission of light. Long trains of waves. Inter- 

 ference with high differences of phase. Structure 

 of spectral lines. Broadening by Doppler effect 

 and other causes. 



Scattering of light by molecules. 



Dispersion of light. 



Anomalous dispersion. Application to solar atmos- 

 phere. 



Gravitation. Propagation and emission of light in 

 a gravitational field. 



Constitution of solid bodies. Atoms held together 

 by electric forces? 



Heat motion in crystals. 



Magnetism. Theories of diamagnetism and para- 



Einstein-effect. 

 Magnetization by rotation. 

 Quantum theory of the Zeeman effect. 



Inverse Zeeman-effect. Older theory. Phenomena 

 observed in the direction inclined to the lines of 

 force. Application to the sun 's magnetic field. 



In addition to the Lorentz lectures, which 

 will be delivered four times a week from 

 January 4 to March 10, Professor Paul Ep- 

 stein will give a course on " The origin and 

 significance of the quantum theory." 



The California Institute of Technology 

 extends a cordial invitation to investigators 

 in physics, and to teachers in universities, 

 colleges and high schools who are able to do 

 so to attend without charge the Lorentz and 

 Epstein lectures, which will be delivered from 

 4 to 6 P.M. in the main lecture room of the 

 Norman Bridge Laboratory of Physics. 



It is probable that before his return to 

 Holland in April Professor Lorentz will spend 

 a week at the University of Chicago and also 

 at several other universities of the West and 

 Middle West. 



THE SECRETARYSHIP OF SIGMA XI 



Professor Henry B. Waed^ of the Univer- 

 sity of Illinois, who has been secretary of 

 Sigma Xi since 1904 and has been in large 

 measure responsible for the national devebp- 

 ment of the Society, writes in the Sigma Xi 

 Quarterly : 



Two years ago when the quarter-century of 

 service terminated, I made an especially urgent 

 appeal that the work be passed to someone else. 

 Just at that time, however, the society was emerg- 

 ing from the chaotic condition in which all organi- 

 zations found themselves after the war, and a new 

 project had just been started which bade fair to 

 arouse interest and develop stronger support than 

 any new plan which the society had developed since 

 the earliest years of its history. It was clear to 

 the president and to the members of the fellowship 

 committee, who were intensely interested in this 

 new movement, that a new man could not possibly 

 take up the work of the secretary 's office without 

 embarrassing very seriously, and delaying or per- 

 haps fatally injuring the campaign for the estab- 

 lishment of Sigma Xi fellowships. Accordingly, I 

 reluctantly consented to carry the work for one 

 more term, with the positive understanding that my 

 resignation, to take effect in December, 1921, would 

 be final. Under these circumstances, I may be par- 



