14 M. M. HAMLET. 



Perhaps the most remarkable discovery in physics during 

 the year is the accumulated and convincing evidence that 

 the particle of radio-active change is an atom of helium, 

 and this point is of fundamental importance in the theory 

 of atomic disintegration and may be considered as now 

 finally settled. At our Sydney University, Prof. Pollock 

 is engaged in the interesting work of the ionisation of the 

 air, and has with his collaborators contributed several 

 papers to the Society on this subject during the year, as 

 well as contributing some interesting exhibits of experi- 

 ments in radioactivity at the Royal Society's conversazione. 

 In the progress of science new methods and ideas are 

 continually appearing, perhaps the most marvellous of late 

 years being the phenomenon of matter spontaneously radi- 

 ating energy into space, and even penetrating other forms 

 of matter, giving rise to changes in atomic constitution ; as 

 already mentioned, the a-particle being ejected into space 

 as the element helium ; thus reviving the prophetic theories 

 of Sir Isaac Newton, and later of Sir William Orookes. 

 In order to prove that an a-particle consists of an atom of 

 helium plus a positive charge, the purified emanation from 

 0*12 gram of radium was compressed into a capillary tube 

 with walls 0*01 mm. thick. This capillary tube was known 

 to be impermeable to helium, but the particle and also 

 radium- A and radium-C could pass through it into a 

 stout outer tube, where the spectrum could be examined. 

 Although, after twenty-four hours no trace of helium was 

 detected, the spectrum gradually developed until, after six 

 days, all the lines of helium could be seen. This helium 

 must have been produced from a-particles which, after 

 traversing the glass, had slowly lost their charge. 1 



In chemistry, Sir William Ramsay has given us a much 

 clearer view of the functions and properties of the electron. 



1 Ernest Rutherford and T. Royds, Phil. Mag., 1909, vi, 17, 281-286. 



