STANDS SCIENCE WHERE SHE DIDr 



By Ivor Thomas 



The 1933 meetings of the British Association, held last month at 

 Leicester, formed a convenient halting place for men of science to 

 look back upon ground definitely won and to survey further territory 

 upon which an attack may be expected imminently. Already they 

 have struck their tents, and are again moving toward the enemy 

 ranks. The attack is being made along the whole line, from the very 

 small to the exceedingly great. But it is at the extremities that the 

 big battalions are concentrated, and reconnoitering parties are daily 

 brinijcinic more and more information both of the structure of the 

 atom and of the nature of the universe as a whole. 



Science thus offers us a kind of Platonic Dyad of the Great and 

 Small, but it is not wholly undetermined. Taking the smaller end 

 first, we may now be fairly confident that there exist four funda- 

 mental particles out of which the whole material universe is com- 

 pacted. There may be others as yet undiscovered, but of these four 

 we may now be quite certain. There is the negative electron, discov- 

 ered in 1897 by Sir J. J. Thomson, which bears, or rather is, a nega- 

 tive charge of electricit}^ Secondly, there is the proton, discovered 

 in 1911 by Lord Rutherford, which is positively charged and has 

 a mass about 1,840 times that of the negative electron. It was 

 thought for a long time that these were the only building bricks in 

 nature, that out of them in suitable numbers and combinations the 

 atoms of all the 92 elements could be formed. The model atom was 

 a miniature solar system with a central nucleus consisting of protons 

 and embedded electrons with a number of electrons circulating in the 

 manner of planets. The number of orbital electrons was such that 

 their electric charge would just cancel out the resultant positive 

 charge on the nucleus, the whole atom being in a state of electrical 

 equilibrium. Tiiis theory was worked out for every element, includ- 

 ing 2 that had not then been discovered, from hydrogen with 1 

 circulating electron to uranium Avith 92. It was proved that the 

 orbital electrons were arranged in groups, and the theory beautifully 

 explained many spectroscopic phenomena and such properties as 

 the conductivity of metals. 



* Reprinted by permission from the Nlnoticnth Century and After, October 1933. 



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