i; 2 SCIENCE PROGRESS 



from one end of the periodic table to the other, from aluminium 

 right into the region of the heaviest elements, worked out by 

 radioactive methods. The total number of distinct chemical 

 elements between hydrogen and uranium is probably ninety- 

 two, and not more than five or six of these remain still unknown. 

 This is an extraordinary testimony to the completeness and 

 thoroughness with which the elements have been investigated 

 by chemists. 



The discussion was continued by Prof. Hicks, who, whilst 

 accepting in general Soddy's theory of the existence of isotopic 

 elements identical with one another in chemical character, 

 pointed out the difficulty in supposing that such elements 

 would prove to be also spectroscopicalty indistinguishable. He 

 had shown that the atomic mass enters directly into the series 

 relationships of spectra. The lines of the very complicated 

 spectrum of thorium, for example, might in some cases be really 

 due to ionium, which would explain the apparent identity of 

 the spectra of ionium and thorium. 



Prof. Nicholson, in a mathematical criticism of the nucleus 

 theory and especially of Bohr's hypothesis, made an interesting 

 reference to coronium, the spectrum of which he had found 

 could be derived accurately on the view that the nuclear charge 

 was five, or the same as that possessed by the terrestrial element 

 boron. He suggested that coronium and other stellar elements 

 might have a type of nucleus entirely distinct from that of the 

 terrestrial elements, and possibly these elements belonged to 

 a different stage in the general evolution of matter. Certainly 

 there is no room in the periodic table, as now understood, 

 for any of the supposed stellar elements, asterium, coronium, 

 nebulium, etc. Prof. Silvanus Thompson raised the question 

 of the magnetic properties of matter and the magneton hypo- 

 thesis, and referred to recent researches of Weiss, which indi- 

 cated that the magnetic properties of the elements differed from 

 one another in such a manner as to be capable of expression by 

 a set of integral numbers. Mr. Allen brought forward some 

 interesting results obtained in the mathematical theory of the 

 nuclear atom, and Sir Ernest Rutherford very briefly replied. 



Municipal Insanitation 



The report upon the state of public health ot the city of 

 Dublin during 1912 issued by Sir Charles Cameron, the Chief 



