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LIII. Intelligence and Miscellaneous Articles. 



ON EXPERIMENTS WITH RONTGEN RAYS. 



To the Editors of the Philosophical Magazine. 



Gentlemen, 



\ LLOTV me to avail myself of your Magazine to make some re- 

 -£*- marks about the Memoirs of Messrs. Ouinoff and Samoiloff 

 (Phil. Mag. October), and of Messrs. J. J. Thomson and Ruther- 

 ford (Phil. Mag. November). 



The experiments of Messrs. Ouraoff and Samoi'loif do not, in 

 my opinion, resemble very closely those of my own experiments on 

 electrical shadows to which they refer, but they have rather much 

 likeness with those, concerning the production of Rontgen's shadows 

 with the electrical method, which I published in two Notes on the 

 1st of March (Rendiconti delta R. Accad. dei Lincei). They have 

 therefore the same analogy with those afterwards published by 

 Prof. Silvanus P. Thompson (Phil. Mag. August). No doubt that 

 Messrs. Ouraoff and Samoi'loff had no knowledge of the previous 

 publications above mentioned. 



As to the Memoir of Messrs. Thomson and Rutherford, I beg 

 to observe that the fact proved at pages 395 and 396 (viz. that 

 a thinner layer of air may offer a greater resistance than a 

 thicker one) has already been described by myself in a Note on 

 the 3rd of May (Bend, delta R. Accad. dei Lincei). In that 

 Note I recalled also some experiments I had formerly made, which 

 proved that an analogous phenomenon may be produced by ultra- 

 violet rays, and also without the action of any radiation at all. 



In the complete Memoir read before the R. Academy of Bologna 

 on the 31st May (" On the Propagation of Electricity through 

 Gases traversed by Rontgen's rays "), I have described with more 

 particulars all these phenomena, and also others that I obtained 

 with Rontgen's rays. 



I am, Gentlemen, 



Tours faithfully, 



Augusto Right, 



Professor of Experimental Physics, 

 in the University. 

 Bologna (Italy), November 1Kb, 1896. 



VOLUME MEASUREMENT OF AN AIR THERMOMETER BULB. 

 BY WALTER G. CADY. 



In all constant volume air thermometry where high tempera- 

 tures are involved, it is frequently necessary to determine the 

 volume of the glass bulb used ; such a bulb softens at a low red 



