6o POPULAR SCIENCE MONTHLY 



positions of the particles within the atom. These rates, however, as 

 measured by the period of decay, vary from thousands of years to a 

 few seconds for the different educts, and that irregularly in the order 

 of transformation — such great differences could only be explained by 

 an infinite number of components, with large free paths, electrons, in 

 other words. It would then remain to be shown what caused a certain 

 great number of negative electrons to form an electro-positive a-particle, 

 and become expelled with great violence from their surroundings. 



Natural^, the failure of a hypothesis to explain certain facts does 

 not invalidate the latter. Eutherford's brilliant analysis of the curves 

 of increasing and decreasing ionization and the agreement observed 

 with calculated results prove that he is not dealing with mere fortuitous 

 coincidences. Many of his conclusions seem incontrovertible upon his 

 premises; but here again, the advocatus diaboli must step in and ask 

 whether the premises are axiomatic: two of them appear to me to be 

 doubtful. (1) A curve of decay is based on electroscopic measurements 

 upon the tacit assumption that the rays sent out by that particular 

 phase are always the same ; but we are told that both a and /? rays vary 

 greatly in speed and momentum, hence neither variety would show a 

 uniform ionizing power ; assuming that a substance did send out a rays 

 for a long time, but that their velocities were gradually reduced, would 

 not the ionization indicate a more rapid decay than was really the case ? 

 (2) It is practically assumed throughout that ionization is directly pro- 

 portioned to the amount of radio-active material present: but this 

 remains to be proven. Where layers of any density are involved, we 

 know that it is not true, owing to internal absorption, etc. ; for ideally 

 thin layers, weighing and other measurement are out of the question. 



I do not think that this latter objection ought to be dismissed 

 lightly, when we find such a phenomenon as the almost universal ioniza- 

 tion of the atmosphere ascribed to the presence of radium or its educts. 

 Thomson himself has shown a variety of ways for ionizing air, when 

 any variation in the amount of radium present — or, rather, absent — is 

 out of the question ; some of these serve particularly well to explain the 

 phenomena in the open air. Eecently, indeed, quite a number of inves- 

 tigators have observed diurnal variations in this atmospheric ionization, 

 sufficiently marked to require some other explanation than the produc- 

 tion of emanations from the earth or surrounding materials. Gustave 

 Le Bon, in his " Evolution de la Matiere," shows how the gold-leaf elec- 

 troscope is discharged when connected with some very dry sulphate of 

 quinine, which is taking up hygroscopic moisture. Are we ready, with 

 him, to assume that the quinine is catalyzing some atoms into nirvana, 

 or that the electroscope may indicate many changes that are not intra- 

 atomic ? 



