UNSUSPECTED EADIATIONS. 373 



have thus been broug-ht into a most intimate connection and hnddled 

 together by these Avonderful radiations. 



Thousands of most delicate experiments have been made and hun- 

 dreds of papers have been written during the last five years, in order 

 to determine the properties and the constitution of these different sorts 

 of rays. Various hypotheses have been advocated, and yet scientific 

 opinion is still hesitating, the more so as new discoveries are made all 

 the time, and they show that we are not yet the masters of the whole 

 series of phenomena brought under our notice. Upon one point only — 

 and a very important one — a certain consensus of opinion begins to be 

 estal)lished; namely, as to the kathode rays. Most explorers, includ- 

 ing Lenard,^ begin to be won to the idea that the kathode raj's are the 

 paths of very minute particles of matter w^hich are thrown at a very 

 great speed from the surface of the kathode and are loaded with elec- 

 tricity. Even under ordinary conditions, when an electric discharge 

 takes place between one metallic electrode and the other under the 

 ordinary atmospheric pressure in a room we see that most muiute par- 

 ticles of the metal are torn off the negative electrode (the kathode) and 

 are transported in the electric spark. Molecules of air join in the 

 stream, creating the w^ell-known "electric wind," and the air path of 

 the electric spark becomes electrified to some extent. The more so 

 when the discharge takes place in the extremely rarefied medium of a 

 \'acuum tube." In this case the molecules of the rarefied gas, as also 

 the metallic particles joining the current, are transported at a much 

 greater speed, and Ave see them as a cone of light. 



That kathode rays are real streams of particles of matter seemed 

 very probable already in 1896, when the subject was discussed in these 

 pages. '^ Recent researches tend to confirm more and more this idea. 

 They act as a real molecular or atomic bombardment and they heat the 

 objects they fall upon; thus, a thin lamella of glass which is placed in 

 their path will be molten.* It is also known from Crookes's experi- 

 ments that when a little mill is placed so as to receive them on its wings 

 it is set in motion, and a back current seems to be originated at the 

 same time, as has been demonstrated by Swinton." They are deflected 

 from their straight path by a magnet and are twisted along the lines 



1 Amialen der Physik, 1898, Vol. LXIV, p. 279. 



-I chiefly follow here Prof. J. J. Thomson, who has explained his views in several 

 articles (Philosophical Magazine, October, 1897, Vol. XLIV, 5th series, p. 293; 1898; 

 Vol. XLVI, p. 528; 1899, Vol. XLVIII, p. 547; also Nature, 1898, Vol. LVIII, p. 8, 

 1900, Vol. LXII, p. 31); and also Dr. L. Zehnder, the author of a Mechanik des 

 Weltalls (1897), in his address before the Freiburg Natural History Society in 1898. 



=* Recent Science, in Nineteenth Century, March, 1896. 



* Goldstein's researches into the compound nature of the cathode rays and their 

 effects deserve a special notice. They are published in several issues of the Annalen 

 der Physik for the last few years. 



^Swinton in Philosophical Magazine, 1898, Vol. XLVI, p. 387; Broca, Comptes 

 Rendus, 1899, Vol. CXXVIII, p. 356. 



