1919] on Ether and Matter 46:d 



we know it, when analysed into constituents, are turning out to be 

 composed each of a definite grouping of ultra-minute particles, the 

 positive and negative electrons, which themselves hardly occupy any 

 space (save as soldiers occupy a country), and which appear to be of 

 two kinds only — the ultimate indivisible units of positive and negative 

 electricity. 



Part II. — The Possible Structure of Atoms, and 

 Their Radiation. 



How then are we to explain the different kinds of matter ? Here 

 we enter upon territory so recently annexed as to be still very 

 debatable ; but progress has been and is still being made, and it is 

 only throLigh the work of recent explorers that we can attempt to 

 answer the question at all. It is invidious to mention names, but I 

 must mention Rutherford, Soddy, Barkla, Bragg, Moseley, Nicholson, 

 and Bohr, among many others. Moseley — as briUiant as anj of 

 them, and patriotically self-sacrificing like all our splendid youth — 

 was killed, alas ! by a' Turkish bullet at Gallipoli ; though not before 

 he had made an immortal discovery. How much more might he not 

 have accomplished had it not seemed good to evil powers to impose 

 by force their dominance on the world ! 



To give a certain and definite answer to questions about the 

 structure of the atom is premature. I can only state the answer 

 which at present tentatively appeals to me, and I think to others. 

 Your Professor of Natural Philosophy (Sir J. J. Thomson) is lecturing 

 I see on Saturday afternoons concerning spectroscopic evidence on 

 this great subject, and he will no doubt carry the matter further. 



Meanwhile, and very briefly, the idea al30ut the atom which at 

 present seems most likely to be on the path towards truth is, a central 

 positive nucleus surrounded by a system of negative electrons — so 

 much is pretty certain — while according to one theory the system is 

 composed of revolving electrons, moving under an inverse-square law 

 in regular orbits, very like the sun and planets. The orbital move- 

 ment is governed by electric force instead of by gravitation, but the 

 laws of motion, and the perturbations which may be caused by outside 

 forces, are very like those familiar to astronomers. 



According to Moseley's experimental counting, and Bohr's theory, 

 hydrogen seems to be like a sun with one planet, just a positive and 

 a negative electron ; the two being equal electrically, but differing in 

 inertia, the positive being the more massive, though probably for 

 that reason the smaller or more concentrated of the two. Helium 

 seems to have two central unbalanced positive charges and two 

 revolving negative ; lithium, three of each ; beryllium, four ; boron, 

 five ; carbon, six ; nitrogen, seven ; oxygen, eight ; and so on, 

 according to the number of the element in Mendeleeff's series— a 

 number something like half the number expressing its atomic weight. 



