i2o POPULAR SCIENCE MONTHLY 



but in addition a number of " enhanced lines," as Lockyer has chosen 

 to call them. By reason of these latter, Lockyer assumes that the 

 atom of iron (as well as of other elements) may consist of more ele- 

 mentary constituents at extremely high temperatures, and, if the cooler 

 vapors could be removed from this hottest zone, the enhanced lines 

 might stand alone for the elementary form of iron — as a proto-iron. 

 Such conditions are said to be obtained in sun spots and our hottest 

 stars. Whether the extremely high temperature alone is sufficient to 

 produce the enhanced lines, or whether their origin lies in the enor- 

 mously rapid changes of electric stress, can not be answered at present. 

 In either case, there seems to be no doubt but that the atom of an 

 element consists of yet smaller particles, which, with rise of the dis- 

 integrating forces, show a marked increase in their activities, and, 

 owing to the similarity existing between these particles, give spectral 

 lines of greater and greater simplicity. 



When a group of lines in a spectrum has oscillation frequencies 

 that obey a single formula we call this group a series. The simplest 

 elements usually give three series, each of which consists of lines in 

 doublets or triplets. The action of a strong magnetic field upon the 

 series of an element's spectrum tends to decompose the series; each 

 line is resolved into two or three lines (doublets or triplets) according 

 as the light is viewed along or across the magnetic lines of force. 

 This is called the Zeeman effect. Of the three components of motion 

 of the particles, that one which lies in the direction of the lines of 

 force with vibrations backwards and forwards can emit no light except 

 when viewed at right angles to these lines of force. The other two 

 motions at right angles to the lines of force suffer a retardation and 

 acceleration, respectively, with the result that their oscillation fre- 

 quencies are similarly affected and consequently two separate lines will 

 be developed. These may be observed by themselves when the light is 

 viewed along the lines of force or in conjunction with the original 

 line — with position between these two — when the light is viewed across 

 the magnetic field. The electro-magnetic composition of the atom 

 therefore seems to be corroborated by these results. 



As an analogy to this gradual disintegration of the atom under the 

 great stress brought to bear upon it, and. further to show how the more 

 complex molecules behave under the influence of temperature, we have 

 only to examine the spectrum of a compound. Whatever compound is 

 admitted into a flame, the characteristic spectrum of the molecule first 

 makes its appearance. This consists not of lines, but of bands of 

 varying widths. On further increase of temperature the decomposi- 

 tion of the compound molecule is attained, and the bands gradually 

 give way to the characteristic lines of the elements concerned. With 

 numerous compounds, for example, the metallic chlorides, this tempera- 

 ture is exceedingly low. Since the presence of spectral lines is un- 



