246 THE rOPULAR SCIENCE MONTHLY 



10 to 45(10)"® sees., depending on the line. The velocity of the cen- 

 ters of Mg A 4481 was found to be about 2.5(10)^ cm. per sec. near 

 the electrodes, dropping to 1.7(10)^ cm. about a millimeter from the 

 electrodes. Air line centers have an existence of about 7(10)"'^ sec. 

 The emission centers in flames and arcs have been studied by Lenard 

 and others. The results obtained do not agree with those found by 

 Stark working with canal rays. 



Negative Electroxs as Emission axd Absorption Centers 

 The Zeeman effect produced b}^ the action of a magnetic field upon 

 the emission or absorption light centers shows that for many spectrum 

 lines of gases and vapors the light center consists of a negative electron 

 and the ratio of the charge to the mass of the electron obtained in this 

 way agrees very well with the value obtained by other methods. The 

 more accurate experiments give e/m = 1.775 while direct experiments 

 give 1.772. 



The Positive Electron 

 The positive electron has never been isolated in any experiment with 

 vacuum-tube discharges, radiations from radioactive materials, etc. The 

 Zeeman effect of certain band spectra of chlorides and fluorides of some 

 of the alkaline earth elements studied by Dufour and of the absorption 

 spectra of neodymium and erbium compounds as studied by Becquerel 

 indicate the existence of positive electrons. These Zeeman effects may 

 be explained, however, as being due to induced magnetic fields being set 

 up in the region of the light centers, magnetic fields whose intensities are 

 very different from the field impressed from without. 



Absorption Centers of Solutions of the Eare Elements 

 Many solutions of salts of elements such as uranium, neodymium, 

 erbium, somarium, etc., show a banded absorption spectrum. Many of 

 these bands are very narrow. Jones, xA.nderson and the writer have 

 found that the absorption centers of many of these salts (e. g., uranous 

 chloride) consist of centers containing the salt and an " atmosphere " 

 of the solvent, the whole center apparently acting as a compound. Thus 

 in the above case it is possible to have " water and alcohol centers " of 

 uranous chloride in a solution of uranous chloride in water and alcohol. 

 Increasing the amount of one solvent appears to increase the relative 

 number of the centers of that solvent without apparently changing their 

 composition. The different solvent centers have different degrees of 

 persistency. The water and alcohol bands of neod}Tnium chloride are 

 of about equal intensity when the salt is dissolved in a solution con- 

 taining about 3 per cent, water and 97 per cent, alcohol. Changes of 

 temperature change the relative persistency of the liglit centers. 



In the case of some uranyl salts the addition of free acid of the salt 

 causes a shift of the bands. This has been explained by the writer as 

 being due to the fact that the light centers consisted of " aggregates " of 



