PHYSICS — BARUS, BURGESS. 247 



X-rays or by a weak sample of radium acting through a sealed tube. 

 It thus appears that the ions or fleeting nuclei resulting are also pro- 

 nouncedly of all sizes within limits, and that the increment of nuclea- 

 tion between two definite degrees of exhaustion (i. e., degrees of 

 sudden cooling) above the fog limit, but not too far from it, is 

 greater as the radiation applied from without is more intense. Vir- 

 tually the gradation of particles is thus more fine-grained or more 

 nearly continuous with the efficient nuclei lying within closer limits 

 of size, as the ionization is more intense. 



Throughout the whole research the important bearing of the solu- 

 tional or water nucleus on the phenomena of condensation has been 

 made manifest. 



The final general result to be referred to here is the readiness with 

 which nuclei are produced by the gamma rays, even after penetrat- 

 ing a centimeter or more of lead, together with the distinction which 

 is thus drawn, experimentally, between these rays and the X-rays. 

 The latter show small penetration, but are so phenomenally active 

 in producing secondary radiation that to a wooden fog-chamber 

 the distance effect for a radius of over 6 meters between bulb and 

 fog-chamber is relatively negligible. The effect of the gamma rays, 

 on the contrary, in spite of the remarkable penetration evidenced, for 

 instance, by the nucleation produced, is nearly vanishing when tested 

 by the same nucleation at a distance of but 50 cm. X- radiation, 

 sufficiently intense to produce persistent nuclei, is accompanied by 

 curiously outspoken distributions, which seem to show either that 

 the nucleation originates in the walls of the vessel or that, in con- 

 sequence of secondary radiation, the density of ionization near the 

 walls is such as to promote rapid growth of nuclei in those parts to 

 abnormal sizes. The nuclei in question are over 200 times more 

 persistent than the ions, and if they decay by breaking into like 

 fragments one may estimate that the former are 5 or 6 times larger in 

 diameter than the latter. Persistent nuclei produced by the X-rays 

 require but a vanishing pressure difference to induce condensation. 

 They have, moreover, the property of increasing in number if left 

 without interference for a short time after radiation ceases. ' 



Burgess, Charles F., University of Wisconsin, Madison, Wisconsin. 

 Grant No. 247. Investigation of the properties of electrolytic iron 

 and its alloys. $2,500. 



Abstract of Report. —The investigation was begun in February, 

 1905, and has been carried on continuously since that time. An 

 outline of the plan which was laid out, and which has been adhered 

 to as closely as possible, is as follows : 



