The same effect has more recently been produced in the case of the spectral rays of nearly—if not quite—all the other elements. The process, as described by Dr. George Ellery Hale, is very simple: “We place our iron ore or spark between the poles of a powerful magnet, and photograph its spectrum. The lines behave in the most diverse way, some splitting into triplets, others into quadruplets, quintuplets, sextuplets, etc. One chromium line is resolved by the magnet into twenty-one components.... The distance between the components of a line is directly proportional to the strength of the magnetic field.”[26] The meaning of this splitting and polarization of light-rays in the magnetic field is that, as Lorentz had predicted, there are present in the luminous vapor vibrating particles negatively charged, or “electrons.” Measurement of the distances apart of the components of the triple line reveals the relation between the charge and the mass of the particles.[27] It is interesting to add that the disturbances in the magnetic field, as observed by Zeeman, were precisely of the amount calculated by Lorentz purely on theoretical grounds, and the mass of the electron was found by this method to be 1/1840 that of the hydrogen atom. By a different method, Sir J. J. Thomson obtained a value of 1/1800 the mass of the hydrogen atom; while Dr. Robert A. Millikan, by means of his famous “electrical balance,” derived a value of 1/1845 that of the hydrogen atom.[28] In his monograph of 1913, Zeeman remarked that in discoveries of optics “we may always cherish the hope that they will lead ultimately to applications to astronomy.” So far as study of solar phenomena and the Zeeman effect are concerned, this hope has been fully realized, and attempts are being made to extend the applications of this method of investigation to other stellar bodies. Of the general value of Zeeman’s discovery, Dr. Hale writes: “The complex phenomena of the Zeeman effect (as revealed in a comparative study, with powerful spectrographs, and an intense magnetic field, of the lines of a long list of elements) furnish material available for wide generalization, important in their bearing on theories of radiation and atomic structure” (_Op. cit._, Page 36). Discovery by Hale and his co-workers at Mount Wilson of the Zeeman effect in sun-spots led to the very important conclusion that these disturbances represent whirling vortices of electrons, producing a magnetic field. “The strength of the magnetic field produced, which is measured by the degree of separation of the triple lines, increases with the diameter of the spot.... It has long been known that sun-spots usually occur in pairs, and our study of the Zeeman effect indicates that the two principal spots in such a group are almost invariably of opposite polarity” (Hale, Op. cit., Pages 28-31).