4 i4 SCIENCE PROGRESS 



gation, we are continually increasing the detail of scientific 

 knowledge. Such detail often leads to valuable results in the 

 practical affairs of everyday life. But there is continually the 

 danger that the mathematician and the physicist should (more 

 or less unknowingly) turn themselves into metaphysicians and 

 give explanations of their results which, to every common-sense 

 mind, are intrinsically and obviously absurd. Any one can do 

 this if they concentrate attention on one small point and ignore 

 the comprehensiveness of reality. When the offender has this 

 concentration combined with a certain degree of positive ignor- 

 ance, we call him a crank. When his facts are newly discovered 

 and such that a high degree of skill is required to note and 

 classify them, he is a not uncommon type of scientific investi- 

 gator, an exponent of ultra-modern physics. 



Let us consider this very question of variable masses. The 

 great axiom is — mass is indestructible, it is impossible for some- 

 thing to become nothing. But an ignorant man could well 

 devise many experiments on seaweed, catgut, wood, any mois- 

 ture-absorbent substance, and demonstrate conclusively that 

 mass varies with the weather or the season of the year. " I 

 have more catgut in winter, weigh it and see," you can imagine 

 him saying. " The fundamental laws of chemistry are wrong." 

 Now while it is perfectly possible to prove that he has not 

 more catgut, but only more or less moisture obtained from the 

 atmosphere, to do so conclusively would be a long and trouble- 

 some analytical process, which the crank would not understand, 

 and to which he could readily make a number of objections. 



The indestructibility of mass, of substance, is simply un- 

 provable. It is an axiom to which we fit our observations. 

 All that chemistry can do is to show that certain apparent 

 changes of mass are only apparent. It traces in detail the 

 distribution of certain masses under certain conditions. 



The point of these observations lies here. Without ex- 

 amining in detail the experiments on the velocities of a and 

 fi rays, we are entitled to say that the experimentalist who 

 mforms us that mass is a function of velocity is giving us 

 information every whit as absurd as the crank who informs us 

 that mass is a function of the season of the year, and more so 

 than the crank who thinks he has discovered a perpetual motion 

 machine. The experiments, no doubt, are valid, but they have 

 been misinterpreted. Sir Oliver Lodge says that there is 



