# Page:Popular Science Monthly Volume 73.djvu/64

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 ${\displaystyle \alpha }$-particle, and become expelled with great violence from their surroundings.
Naturally, the failure of a hypothesis to explain certain facts does not invalidate the latter. Rutherford'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 ${\displaystyle \alpha }$ and ${\displaystyle \beta }$ rays vary greatly in speed and momentum, hence neither variety would show a uniform ionizing power; assuming that a substance did send out ${\displaystyle \alpha }$ 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 proportioned 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.