Dbokmbkr 7, 1900.] 



SCIENCE. 



A curious fact, assuming the truth of the fol- 

 lowing hypothesis, is that the energy of a mov- 

 ing body is not proportional to the square of its 

 velocity, but exceeds this by an amount which 

 becomes infinite when the body attains the 

 velocity of light, although this excess of energy 

 at ordinary velocities is exceedingly small. If 

 it were not for the tendency of electrical field 

 to become concentrated in a certain plane as 

 described above, the energy of a moving body 

 would be strictly proportional to the square of 

 the velocity, assuming the truth of the hypothe- 

 sis which is now to be stated. 



The excess inertia due to the electric charge 

 on a body, or briefly, the inertia of the charge 

 is greater and greater the smaller the body. 

 Atoms, however, are not small enough for us 

 to attribute all their inertia to the charge which 

 they carry when they are in the form of ions. 

 The corpuscles, of which J. J. Thomson builds 

 an atom like a bricklayer builds a house, and 

 to the hypothetical existence of which Thomson 

 was led by the study of cathode rays, are per- 

 haps small enough. 



The electrical hypothesis of the constitution 

 of matter, is that atoms of matter are built up 

 of corpuscles, and that these corpuscles are mere 

 bits of electric charge, some positive and some 

 negative surrounded by electric fields, or rather 

 that these corpuscles are mere strain centers in 

 the ether surrounded by regions of ether stress. 



This hypothesis of the constitution of matter 

 serves well for the interpretation of the per- 

 plexing class of phenomena attending the dis- 

 charge of electricity through gases and it 

 explains that fundamental property of matter, 

 inertia. 



Now we have two distinct measures of mass, 

 namely : One body is said to be twice as mas- 

 sive as another, or to contain twice as much 

 matter, when it is accelerated at half as great a 

 rate by the same force or when it is attracted by 

 the earth or any third body by twice as great a 

 force. The first measure of mass is sometimes 

 called inertia and the second is often, in daily- 

 life, called weight, and it is I'emarkable that 

 these two measures agree with each other to a 

 great degree of precision. One might expect, 

 therefore, that an hypothesis as to the constitu- 

 tion of matter which clears up the nature of 



inertia, even provisionally, would throw some 

 light upon the nature of gravitation, but it does 

 not seem to be so, and Professor Fessenden 

 must needs say more from his point of view and 

 with greater precision before we shall be con- 

 vinced. The difficulty to be encountered in the 

 explanation of gravitation from the point of 

 view of the electron hypothesis, as Johnstone 

 Stoney calls it, seems to be as follows : 



Imagine all corpuscles to consist of equal 

 positive or negative charges, this indeed is as- 

 sumed by J. J. Thomson, the only present 

 need of this assumption is to permit of simple 

 statements. Then, if those approximate facts 

 which we call the laws of electrostatics were 

 true, Newton's law of gravitation (?) would 

 have to do only with electric attraction and re- 

 pulsion, and it would run thus : every corpuscle 

 of matter in the universe attracts or repels 

 every other particle with a force which is in- 

 versely proportional to the square of the dis- 

 tance between them. 



Two opposite charges may be said to be equal 

 in value when they are acted upon by equal and 

 opposite forces when placed in a uniform elec- 

 tric field. Now if two such charges of opposite 

 sign attract each other with a slightly greater 

 force than the force of repulsion of two precisely 

 equal charges of the same sign, then two aggre- 

 gations of equal numbers of positive and neg- 

 ative corpuscles would on the whole attract each 

 other, because the oppositely charged corpus- 

 cles in the two aggregations would attract each 

 other a little more than the similarly charged 

 corpuscles would repel. Thus gravitation would 

 be due to the fact that the attraction of equal 

 and opposite charges would be slightly greater 

 than the repulsion of like charges of the same 

 value. This inequality of attraction and re- 

 pulsion of equal charges would exist if the re- 

 lation between stress and strain in the ether 

 were not a linear relation, that is, if ether 

 strain were not proportional to ether stress, for 

 in the case of opposite charges the ether stresses 

 are on the whole more intense and less widely 

 distributed than are the ether stresses in case 

 of two like charges of the same value at the 

 same distance apart. It would be a compara- 

 tively simple matter to determine the amount 

 of deviation from proportionality of stress and 



