444 THE POPULAR SCIENCE MONTHLY 



couple of years his theory was claiming the attention of a number of 

 prominent mathematicians and physicists. Minkowski, a German 

 mathematician of the first rank, just at this time turning his atten- 

 tion to mathematical physics, came out in 1909 with his famous world 

 postulate, which has been briefly described. It is interesting to note 

 that within a year translations of Minkowski's article appeared in Eng- 

 lish, French and Italian, and that extensions of his theories have occu- 

 pied the attention of a number of Germany's most famous mathema- 

 ticians. Next Poincare, perhaps the most brilliant mathematician 

 of the last quarter century, stamped the relativity theory with the un- 

 official approval of French science, and Lorentz, of Holland, one of the 

 most famous in a land of famous physicists, aided materially to the de- 

 velopment of the subject. Thus we find within five years of the ap- 

 pearance of Einstein's article, a fairly consistent body of doctrine 

 developed, and accepted to a surprising degree by many of the promi- 

 nent mathematical physicists of the foremost scientific nations. No 

 sooner was the theory in a fairly satisfactory condition, than the at- 

 tempt was made to verify some of the hypotheses by direct experiment. 

 Naturally the difficulties in the way of such experimental verification 

 were very great — insurmountable in fact for many experiments, since 

 no two observers could move relative to each other with a velocity ap- 

 proaching that of light. But the change in mass of a moving electron 

 could be measured, and a qualitative experiment by Kaufmann, and 

 a quantitative one by Bucherer gave results which were in good agree- 

 ment with the theoretical equations. It was the hope of the astron- 

 omers that the new theory would account for the long-outstanding 

 disagreement between the calculated and the observed motion of Mer- 

 cury's perihelion, but while the relativity mechanics gave a correction 

 in the right direction, it was not sufficient. To bring this very brief 

 historical sketch down to the present time, it will perhaps be sufficient 

 to state that this theory is at present claiming the attention of a large 

 number of prominent mathematicians and physicists. The details are 

 being worked out, the postulates are being subjected to careful mathe- 

 matical investigation, and every opportunity is being taken to sub- 

 stantiate experimentally those portions of the theory which admit of 

 experimental verification. Practically all of the work which has been 

 done is scattered through research journals in some six languages, bo 

 that it is not very accessible. Some idea of the number of articles pub- 

 lished may be obtained from the fact that a certain incomplete bibliog- 

 raphy contains the names of some fifty-odd articles, all devoted to some 

 phase of this subject — varying all the way from the soundest mathe- 

 matical treatment, at the one end of the scale, to the most absurd 

 philosophical discussion at the other. And these fifty or more articles 

 include only those in three languages, only those which an ordinary 



