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atom ought to be constant and to appear in all phenomena where we are concerned directly with electrons. a matter of fact, i t varies from 1.865 X 107 (cathode rays) to 3.j34 X 1 0 7 (Zeenian effect) and even reaches the value of 1.656 X 1oS in the crystalline absorption. These discrepancies cannot be explained as due to differences in velocity for these could only increase the value of m and diminish t h a t of the ratio' e l m "In spite of these anomalies, the electromagnetic theory of the cathodic pheiioniena constitutes a marked advance, the greatest that has been made in this branch of physics since the work of Sir IT., Crookes." * Pellat has recently suggested a veri- simple explanation of these variations in e / ? n (Comptes rendus, 145,6 7 3 (1907)). Il'ilder 13.I i a ? z c r ~ j f Recherches theoriques et experimentales sur la Constitution des Spectres ultraviolets d'Etincelles oscillantes Lij' EiLgbne .YPczdcPcr. 2.j X a8 cm; p p . azo. Paris: A . Hermatin, 1903. Pyice: paper> 1 2 jmncs.-This volume colitains a n account of work begun in 1901. The author summarizes his conclusions a s follows: "The object of this investigation was to study the efiect of self-induction on the oscillating discharge with reference to the changes produced in the extreme ultra-violet portion ( i = z;oo-rmo Angstrom units) of the spectra of the metals forming the electrodes b e t w e n which pass the sparks coming from the discharge of a condenser. At every step there were so many experimental difficulties in the spectrographic study of this invisible region of the spectrum t h a t i t has been necessary t o devote a portion of this investigation to the theory of spectroscopic instruments h s e d on physical optics, a theory not very familiar t o spectroscopists, yet which throws a clear light on a number of apparently obscure points concerning the chuice and action of a spectroscopic instrument. d s a result of setting forth this theory as doctrine, it is hoped that people will finally give u p completely the old views, based on geometrical optics, which are entirely insufficient to give a definite account of the exact way in which a spectroscopic instrument acts. "11-e may sun1 up, as follows, our results on the effect of self-induction on the extreme ultra-violet portion of the spark spectra: I . Self-induction has a very powerful effect in the extreme ultra-violet region of the spark spectra of the metals we have studied: TI, P b , Bi, Sn,Sb, Cu, -Ig,Ti, Fe. 2 . The different ultra-violet lines of the metals just mentioned can be divided into three groups with reference to the variation of intensity when there is an increase of self-induction in the discharging circuit. The first-class includes those lines which weaken very rapidly with increasing self-induction. The second class includes those lines which only weaken gradually as the selfinduction increases. The third class includes the lines whose intensities pass through maxinia and minima as the self-induction of the circuit increases. This entirely natural classification of the lines was proposed by Hernsalech for the visible region of the spark spectra. I t is also valuable for the ultra-violet portion of the spectrum. 3. These three classes of lines may exist separately in the spectra studied.
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As a rule the lines corresponding to the first and second classes are the most common. Lines belonging to the third class are not common in the region we have studied. 4. Lines belonging to the harmonic series of Kayser and Runge never belong to the second class, which i s quite contrary to what Hemsalech established in his thesis of 1901 ; b u t they often belong to the first and sometimes to the third class. j. On the other hand the doublets of Rydberg and the triplets of Kayser belong almost exclusively to the second class. 6. TVe may adopt the following hypothesis in regard to the mechanism of the effect of self-induction on the intensity of the lines. The self-induction modifies the frequency and the intensity of the oscillations of the condenser discharge, with the result that the forced vibrations due to the luminous atoms change and cause the intensification of certain rays or the JTeakening of others. The capacity will increase the density of the metallic vapor and v-ill probably cause a rise of temperature. Some physicists even believe t h a t they have noticed a modification of the spectra due t o this. Our actual knoLv1edge of the luminous emission of a nietallic vapor excited by the electric discharge is so incomplete t h a t i t is impossible to formulate a sufficiently complete explanation of the effect on the intensity of the spectral lines produced by changes of the electrical conditions in the discharging circuit. ;. TVe have obtained very interesting results in the ultra-violet portion of the spark spectrum of titanium. TVe have been able to detect real series of ~Izortlines, n.hich appear in a very clear manner. 5. This effect of self-induction on the character of spectral lines due t o oscillating sparks may serve to indicate in some cases the harmonic relations existing between certain lines of the same spectrum. TVe therefore have the following methods of studying the character of a line or a series of lines. (a) S f u d y o j Their rippeavaiice.-IVe classify the lines as reversed, diffuse, short, etc. This method has already been employed for the reversed lines of palladium and the diffuse lines of copper. Unfortunately the appearance of the lines depends on a number of external circumstances such as the resolving power of the spectroscope, the density and temperature of the metallic vapor, the time which the photographic plates are exposed, etc. The effect of all these things must he taken into account in any such comparison as suggested. ( b ) Effect of Temperature.-There are lines which become more intense or xeaker for a given rise of temperature. l y e distinguish arc lines, spark lines, the enhanced lines of Lockyer, etc. (c) Eiject e j P~essure.--Humphreys and 3Iohler have shown t h a t pressure has a selective action on the different lines of a n element; b u t their investigations do not cover all the lines of any spectrum. ( d ) The Zeemaiz Pheizowzenen.-TTe investigate the effect of a magnetic field on the different lines of a spectrum. study the same spectrum in different gaseous (e) Crew’.? .\fethod.-TTe media.
(f).-lction of Selj-induction.-FinaIly, x e may employ the method xhich has been the subject of this investigation.” II’ilder D . Bancrojt
