558 



SCIENCE 



[N. S. Vol. XXVI. No. 669 



powder exploded. The cars were blown to 

 bits, rails were broken and warped and the 

 pieces were hurled to great distances; houses 

 in the vicinity were wrecked; and the force 

 of the explosion was felt throughout the city. 

 The seismographs recorded the surface move- 

 ment as a cross tracing, distinct but suscept- 

 ible of measurement only with the aid of a 

 lens. 



J. E. Talmage 



MASS AND ENERGY 



The following is an outline of some inter- 

 esting theoretical results, a full account of 

 which will shortly appear elsewhere. 



If a piece of matter be considered as an 

 electrical system, possessing any structure or 

 internal motions, but having on the whole a 

 kind of average symmetry, then it may be 

 shown that the electromagnetic mass of such 

 a system for ordinary velocities is given by 



4 1 

 Mass = -y^ E 



where V is the velocity of light and E is the 

 total electromagnetic energy of the system. 

 Thus the mass of the system is determined 

 solely by its energy content, and the idea is 

 suggested that mass and energy may have 

 something in common. This result has sev- 

 eral interesting implications. 



Any reaction which is caused by the action 

 of electric forces will involve a change in the 

 electromagnetic energy content of the system, 

 and hence according to the above view will be 

 accompanied by a change of mass. This 

 change will, of course, in general be a de- 

 crease. In the case of ordinary chemical re- 

 actions calculation shows that this change 

 would .be too small to be detected, but in the 

 case of radioactivity, where the energy lost is 

 relatively much gTcater, a sensible change is 

 to be expected. Thus on this view the atomic 

 weight of the various products of radium can 

 not be accurately calculated from the number 

 of a-particles lost, for there is this further de- 

 crease in mass due to the loss of energy. 



The evolutionary theory of the elements has 

 always met an almost insuperable difficulty in 



the fact that there appears to be no exact 

 regularity of any kind throughout the list of 

 atomic weights. 



Some years ago Rydberg came to the con- 

 clusion that it was necessary to consider the 

 atomic weights, up to that of iron, as made 

 up of two distinct parts N -{- D, where i> is a 

 very small difference, a slight deviation in fact 

 from (N). Exact harmonious relations exist 

 between the various N's and Eydberg seems 

 to consider the D's as representing real phys- 

 ical deviations and not merely mathematical 

 remainders. 



From, the point of view of loss of mass ac- 

 companying energy dissipation, it is evident 

 that these small irregularities are just what 

 is to be expected. 



Finally it is to be noticed that if for all 

 matter the ratio of mass to weight is sensibly 

 the same, the above mentioned proportionality 

 between mass and included energy can only 

 imply that the gravitation of a body is always 

 proportional to its total energy content, and 

 this constant proportionality seems to point 

 toward the conclusion that it is confined 

 energy which gravitates and not mass in any 

 other sense. 



It is perhaps well to point out that the con- 

 elusion respecting gravitation involves the as- 

 sumption that all the mass of matter is electro- 

 magnetic, while the conclusion respecting loss 

 of mass and atomic weight irregularities re- 

 quires only that the forces causing the energy 

 change be electric or magnetic, i. e., requires 

 only that part of the total mass be of electro- 

 magnetic origin. 



Daniel F. Comstock 



Mass. Institute of Technology, 

 September 9, 1907 



NOTES ON ENTOMOLOGY 

 Another heavy installment of Wytsman's 

 " Genera Insectorum," has made its appear- 

 ance. Fascicle 46'= by Otto Schwarz com- 

 pletes the Elateridse or click beetles; it com- 

 prises pages 225 to 370, and six colored plates. 

 The types of the genera are not indicated, 

 and the references are incomplete. In the 

 case of new genera there is nothing to show 



