l8 PRESIDENTIAL ADDRESS. — SECTION I. 



V = h m V- and (2) that due to the energy expended in producing 



e- V- 



the magnetic field = h 



" r 



.-. I m V- + \ - = I \m + % — ] v 



■^ y - \ r ' 



— that is. the mass is apparently increased by an amount pro- 



portional to §- or an electrified particle has practically a greater 



mass than an unelectrified one. Now, if the particle is very small 

 and the velocity great the increase in mass will be large and, for 

 a given charge, the increase will be greater for a small body than 

 for a large one, so that the extra mass due to the motion of the 

 corpuscle becomes greater and greater in proportion to the original 

 mass until at last the greater part of the energy will be used in the 

 work done on the charge. Finally, the whole mass of the corpuscle 

 behaves as though it were of electrical origin. If this is true for all 

 corpuscles and if all matter is made up of corpuscles then the 

 logical conclusion is that the mass of all matter takes its origin in 

 charges of electricit3^ 



The size of a corpuscle is much smaller than that of an atom. 

 The linear dimension is about 10^^^ cm., while that of the atom 

 is of the order lo"*^ — that is, the atom is 100,000 times the size of 

 the corpuscle. The volume of the corpuscle is thus very small 

 compared with the volume of the atom. To give some sort of 

 parallel so as to compare the ratio of the size of the corpuscle to 

 that of the atom, it may be stated that the size of the earth is to 

 the size of its orbit of the order of i to 24,000, so that the corpuscle 

 in comparison with the atom is only one quarter as great as is the 

 earth to its orbit. If there is a number of corpuscles in an atom, 

 the distance between each must be great as compared with their 

 radii. Following the conventional idea that matter is composed 

 of atoms, we say that atoms are all of one size but possess different 

 weights, and to each atom a definite number known as the atomic 

 weight is assigned. This number is, of course, purely a relative 

 one, and when we say that " the atomic weight of an element is 

 20 " we simply mean that taking the hydrogen atom as unity, 

 this particular atom weighs twenty times as much. The actual 

 mass of the atom is exceedingly small, being somewhat of the 

 order of 10 -^ grms. No chemical explanation as to the cause 

 of the different values of the atomic weight has, so far as I know, 

 ever been given — the periodic law classifies but does not explain. 

 We have been in the habit of considering them as " constants of 

 Nature." They certainly are constant in value, for if this were 

 not the case quantitative chemical analysis would be impossible. 

 An explanation has been put forward by Professor J. J. Thomson, 

 based upon the corpuscular theory of matter. He has suggested 

 that the number of corpuscles associated with each atom of matter 

 is the same as the number expressing the atomic weight. Should 

 this bear the test of investigation, it will be one of the most remark- 

 able discoveries of recent years, and, whilst further proving the 

 corpuscular theory of matter, will also give a real meaning for the 

 values attached to the atomic weights. 



