THE UNDERLYING FACTS OF SCIENCE 573 



what is known as " periodic acceleration," pulsation or vibration. We 

 can not measure a uniform motion in a particle moving with the speed 

 of light, but we can measure its acceleration. All forces pulsate; they 

 are all propagated as waves, which set up vibratory motions in matter 

 and thus make their presence evident. 



In support of this statement about the nature of mass, which is of 

 such fundamental importance, the words of Professor Kutherford may 

 be quoted : 



If a charge of electricity in motion exactly simulates the properties of 

 mechanical mass, it is possible that the mass of .matter in general may be 

 electrical in origin and may result from the movement of the electrons con- 

 stituting the molecules of matter. 



It is to be noticed that Professor Eutherford refers to the electrons 

 as charges of electricity. His words give a full, if concise, definition of 

 the electrical theory of matter which is accepted by the mass of physi- 

 cists and of which Sir Oliver Lodge is the able historian. When Davy 

 suggested that matter and electricity were kindred phenomena he could 

 hardly have suspected how near he was to the truth as it is seen to-day. 

 The materialists and energists are now on the high-road to reconcilia- 

 tion, and we are permitted to feel that an explanation may soon be 

 forthcoming for the well-known relation between specific heat and 

 atomic weight, and for that existing between spectral phenomena and 

 atomic weight. 



The matter of gravitation can not be put aside without a few addi- 

 tional remarks. Lord Kelvin, by calculation, has ascribed to the ether 

 a weight of one-thousand-billionth of a gram per cubic meter. This 

 is not very much, and can give little encouragement to Lothar Meyer's 

 suggestion that the slight divergences between theoretical and actual 

 atomic weights in the periodic system may be due to the imprisonment 

 of a quantity of the ether within matter ; as just suggested, these differ- 

 ences are more likely due to electronic losses. 



If the new theory of mass is accepted we must postulate a quantity 

 of energy in the ether in keeping with its weight. We shall know more 

 about this when these quantities have been calculated by different indi- 

 rect methods and the results compared. We shall have occasion, a little 

 later, to discuss the temperature of space between which and its internal 

 energy and mass some relation may exist. Heat is usually considered 

 to be due to atomic agitation; we are now assuming mass to be due, 

 possibly, to corpuscular agitation, which already produces, as we know, 

 light and other electro-magnetic phenomena. The day may come when, 

 able to control the internal forces of the atom and effect transmutations, 

 man may set about destrojang matter, as such, altogether, for use in his 

 industries at so much per kilowatt-hour. To the peculiar forms of 

 insanity which induce some men to sell eternal salvation and others 



