84 



SCIENCE 



[N. S. Vol. XXX. No. 759 



At Swartlimore College, Mr. Louis Fussell, 

 instructor in electrical engineering and Mr. 

 Koss W. Marriott, instructor in mathematics, 

 have been promoted to assistant professor- 

 ships. Mr. H. L. Ward, who has been assis- 

 tant at Yale University, has been appointed 

 instructor in chemistry. 



Mr. George P. Paine, of Eipon College, has 

 been made assistant professor of mathematics 

 at the University of Minnesota. 



Dr. Jonathan T. Korer, of the Central 

 High School, Philadelphia, has been called to 

 the headship of the mathematical department 

 of the new William Penn High School for 

 Girls, of the same city. 



The chair of botany at Birmingham, vacant 

 by the retirement of Professor Hillhouse, has 

 been filled by the appointment of Dr. G. S. 

 West, who for the past four years has been 

 lecturer in botany at the university. 



Mr. James Colquhoun Irvine, Ph.D. (Leip- 

 zig), D.Sc. (St. Andrews), has been appointed 

 to the chair of chemistry in the University of 

 St. Andrews in place of Professor Purdie. 



DISCUSSION AND CORRESPONDENCE 

 THE FUNDAMENTAL LAWS OP MATTER AND ENERGY 



To THE Editor of Science: In a late num- 

 ber of Science (April 23, 1909) Professor 

 Speyers has raised some objections to the sys- 

 tem of non-Newtonian mechanics which I 

 recently published.' While some of these ob- 

 jections are due to misunderstanding of the 

 method employed in developing the new sys- 

 tem, others of an a priori character are based 

 apparently upon a certain feeling of repug- 

 nance to the view that the velocity of light in 

 vacuo possesses a unique significance, as the 

 limit of all possible velocities in a material 

 system. This feeling, which has been expressed 

 by numerous critics of non-Newtonian me- 

 chanics, I should like to discuss briefly. I will 

 take this opportunity also to present in a new 

 and perhaps simpler way, the principles in- 

 volved in the development of the new system 

 of mechanics. 



" Technology Quarterly, June, 1908 ; Philosoph- 

 ical Magazine, 16, 705. 



We may base our whole argument merely 

 upon four empirical laws, of which the first 

 two are universally accepted and form an 

 essential part of the foundation of physical 

 science. The other two are more specific in 

 character, but it is hardly likely that their 

 validity will be questioned by any one. 



The first is the law of conservation of mass. 

 If a system gains in mass, its environment 

 must lose in mass by the same amount. 



The second law states that if the center of 

 mass of a given system is at rest, it can not 

 be set in motion except through the agency 

 of an external force; in other words, if the 

 center of mass of an isolated system is at rest, 

 it will remain at rest. 



The third law was deduced by Maxwell from 

 electromagnetic principles, by Boltzmann from 

 thermodynamics, and has been accurately veri- 

 fied experimentally by Nichols and HuU. It 

 concerns the mechanical impulse experienced 

 during the absorption or emission of light. 

 If a body emits a beam of parallel light, it 

 acquires momentum in the opposite direction 

 and the momentum acquired is equal to E/V; 

 where E is the quantity of energy emitted, 

 and V is the velocity of light. 



The fourth law has always been tacitly as- 

 sumed and I name it here only to show with 

 particularity the whole empirical basis upon 

 which the system of non-Newtonian mechanics 

 rests. This law states that if a body suffers 

 a mere loss of energy through radiation, and 

 if then the same amount of energy is returned 

 to it by thermal conduction, or by an electric 

 heater, or by friction, or in any other such 

 way, the system will return to its original 

 condition. 



Let us now consider, isolated in space, a 

 body at rest. For an instant this body emits 

 a beam of parallel light directly away from its 

 center of mass. As a consequence of the pres- 

 sure of the emitted light, the body begins to 

 move in the opposite direction, acquiring mo- 

 mentum which is equal to E/V, E being the 

 energy of the small quantity of radiation 

 which is now traveling away from the original 

 center of mass of the system with a velocity V. 



If the velocity acquired by the body is v 



