xii I'kOCKI.DINC.S. [Decanbcr 2Jid,igij. 



account for the production of such swift hydrogen atoms as 

 are observed, the centres of the two nucleii must approacli 

 within a distance of each other of 2 x lo"''' cms. This 

 distance is about tlie same magnitude as the diameter of the 

 electron. Remembering that this gives a maximum estimate ot 

 the diameter of the nucleus of the hydrogen or helium atom, it 

 is obvious that the nucleus must have exceedingly small dimen- 

 sions. If the mass of the hydrogen atom is electromagnetic in 

 origin, according to present theories, it should have a diameter 

 al)out 1/1800 of the diameter of the electron. While at present 

 tliere is no experimental evidence to give a minimum estimate 

 of the diameter of the hydrogen nucleus, it does not seem 

 improbable that it may have the minute dimensions necessary 

 for its mass to be entirely electromagnetic in origin. On such 

 a view the charged hydrogen atom is to be regarded as the 

 positive electron. Such a view has been proposed at various 

 times, and the proof of the minute dimensions of the hydrogen 

 nucleus certainly adds weight to this suggestion. 



It has recently been suggested by A. van der Broek and 

 Bohr that the charge on the nucleus is not given by a number 

 equal to half the atomic weight but is equal to the number of 

 the element when arranged in a series of increasing atomic 

 weights. On this view\ for example, the charges on the nucleii 

 are for hydrogen, helium, lithium, carbon and oxygen i, 2, 3, 6, 

 and 8, respectively. The experimental evidence is distinctly in 

 favour of this view, and it has been supported by the recent 

 experiments of Moseley in The Philosophical Magazine. A brief 

 account was given of the attempts made by Bohr and others to 

 explain in detail the constitution of the simple atoms and the 

 spectra to which they give rise. It was pointed out that the 

 chemical and physical properties of the atom are ultimately 

 determined by the charge on the nucleus, which should con- 

 sequently be a more fundamental constant than the atomic 

 weight. The latter will depend on the inner structure of the 

 nucleus, and may not be proportional to the charge on the 

 neuclns 



