C. Barus — Distribution of Nuclei. 



175 



Art. -XI. — Preliminary Results with an Objective Method 

 of Showing Distribution of Nuclei Produced by the 

 X-rays, for Instance / by C. Bartts. 



[The present research was carried out experimentally by Eobinson Pierce, 

 Jr. , and myself, and I would gladly associate his name with mine at the 

 head of this article, did he permit it. J 



1. Introductory. — By passing the X-rays into one end of a 

 long rectangular (virtually tubular) condensation chamber and 

 observing the effect produced after successive different inter- 

 vals of time by the condensation method, evidence with a 

 possible bearing on the origin of these nuclei was obtained. 

 The coronas are distorted and at first occur on the bulb side of 

 the apparatus only. The distribution of nuclei is inferred 

 from the form of the corona. 



The experiments described were all made with strictly dust- 

 free saturated moist air, as both the method of precipitation 



and of filtration were applied prior to each experiment, and 

 the exhaustion carried to a higher degree in the purifications 

 than in the measurement. Furthermore as the exhaustions 

 necessitated the use of short lengths of rubber tubing (1/2, 

 3/1, and 1 inch in bore in the different cases), the amount of 

 cooling obtained does not directly correspond with the pressure 

 difference, Sp, owing to the resistance of the tube to the flow 

 of air. The data, op, each refer to a given type of apparatus 

 but are satisfactory as relations, so long as this is not changed. 

 Furthermore the 8p was so adjusted as to entrap all X-ray 

 nuclei, to the exclusion of the normal, quasi-molecular nuclei 

 of dust-free air. 



2. Apparatus. — The method was purposely reduced to 

 extreme simplicity and the apparatus is shown in the annexed 

 diagram. AD is the long rectangular condensation chamber 

 of wood impregnated with resinous cement. The front and 

 rear faces are plate glass through which the coronas may be 

 observed. The other sides are lined within with thick cotton 

 cloth, kept wet, and there is a layer of water at the bottom to 



