472 Henry Andrews Bumstead. 



lead is approximately double that produced in zinc. The 

 only plausible explanation was that the rays effected a 

 disintegration of the lead atoms through which they 

 passed, liberating energy which was then converted into 

 heat. This result, if true, would have constituted the 

 first successful attempt to effect an artificial disintegra- 

 tion of the atom. Unfortunately, however, the subse- 

 quent work of Angerer and of Bumstead himself failed to 

 confirm the results of the earlier experiment. By 

 varying the conditions of the experiment Bumstead 

 was"^ able to show that the differential effect observed in 

 the first instance was due to faulty heat-insulation of the 

 metals under investigation. 



In the meantime Bumstead had returned to New Haven 

 to succeed Professor A. W. Wright as Professor of 

 Physics in Yale College and Director of the Sloane Labor- 

 atory. He soon realized the inadequacy of the old 

 Physics Laboratory, and it was largely as a result of his 

 efforts that William D. Sloane and Henry T. Sloane of 

 New York were persuaded to give to the University and 

 to endow generously the present commodious building. 

 All those Avho have benefited by the facilities and conve- 

 niences of the new laboratory are under a great debt of 

 gratitude to Professor Bumstead for his many months of 

 painstaking planning and careful supervision of the erec- 

 tion of the building. In this new laboratory were housed 

 together, for the first time, both undergraduate depart- 

 ments of study in a single subject This union was the 

 forerunner of the departmentalization which has been so 

 prominent a feature of the recent L^niversity reorgani- 

 zation. 



In 1905 appeared Einstein's epoch-making paper on the 

 principle of relativity. Always interested in electromag- 

 netic theories, Bumstead 's mind was greatly stimulated 

 by the new principle. In 1908 he published a critical 

 comparison of the view-points of Einstein and Lorentz, 

 and devised elegant methods of deducing some of the 

 consequences of the theory. In particular, mention should 

 be made of his derivation of the ratio of longitudinal to 

 transverse mass from a simple consideration of the period 

 of a moving torsion pendulum. In this paper he made 

 some attempt to extend Einstein's method to gravitar 

 tional problems, and pointed out clearly the fallacy of the 

 oft-repeated assertion that a finite velocity of propagation 



