UNSLT8PECTED RADIATIONS.^ 



By Peinck Kropotkin. 



The sensation created live years ago l\y the discovery of the Ront- 

 gen rays had hardly begun to subside, and the patient, minute explo- 

 ration of the newly opened tield was only just beginning, when new, 

 and new discoveries of formerly unsuspected radiations, came to add to 

 the already great complexity of the phenomena, upsetting the provi- 

 sional generalizations, I'aising new problems, and preparing the mind 

 for further discoveries of a still more puzzling character. At the 

 present time the physicist has to account for not only the kathode and 

 the X or Rontgen rays, but also for the '"secondary " or *'S-rays'' of 

 Sagnac, the "Goldstein rays,'' the "•Becquerel rays," and, in fact, for 

 all the radiations belonging to the immens(> border land between elec- 

 tricity and light. Nay, most fundamental ([uestions concerning the 

 intimate structure of matter are being raised in connection with these 

 investigations, and the physicist can not elude them any longer, 

 l)ecause one of his most important principles, estal)lished l)y Car not 

 and generally recognized since, seems also to require^ revision, or has, 

 at least, to receive a new interpretation. 



So many different "rays" are now under consideration that it is 

 necessary to begin by well defining them in a few words, even at the 

 risk of repeating things already said in these pages and generally 

 known. The ''vacuum tube "is the starting point for all new radia- 

 tions, and in its simplest form it is, as is known, a sealed glass tube, 

 out of which the air has been pumped, and which has at each 

 end a piece of platinum wire passed through the glass and entering 

 the tube. When these two wires are connected with the two 

 poles of an induction coil, or the electrodes of an influence elec- 

 trical machine, or a powerful battery, they become poles them- 

 sehes. The tube begins to glow with a beautiful light, and a stream 

 of luminous matter fiows from its negative pole — the kathode— to 

 the positive pole. These are the kathode rays, the detailed explora- 

 tion of which was begun years ago by Hittorf, but won a special 

 interest when Crookes took them in hand, and once more when the 



'Reprinted from The Nineteentli Century, No. 286, December, 1900, by permis- 

 sion of Leonard Scott PnbHeation Company. 



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