1909.] OF VARIOUS SALTS IX SOLUTION. 217 



and probably have characteristic spectra. (12) The final product is 

 lead, *\vhich has a very complex spark and arc spectra. During 

 these transformations several electrons have been thrown off from 

 the various products with enormous velocities. In a very large 

 number of the above spectrum lines the Zeeman effect indicates the 

 presence of negative electrons and charged doublets. 



We thus see what an extremely complex system UO2 must be 

 and it might seem almost hopeless to entangle the mystery of its 

 various spectra. At present we know that the arc and spark 

 spectra problem is very complex and that we have very few methods 

 of producing any changes in it. Practically the only method of 

 changing the frequency of these vibrations is by applying a very 

 powerful magnetic field or great pressure and these changes in the 

 frequency are very small. One very important result, however, 

 has been accomplished by Kayser, Runge, Wood and others. This 

 work consists in separating spectrum lines into various series. A 

 series of lines are those whose intensity and Zeeman effect vary 

 in the same way when the conditions outside the atom are changed. 

 The work of Wood is very important and shows that spectrum 

 lines are due to different systems of vibrators inside the atom. 

 By using monochromatic light of different wave-lengths he has been 

 able to excite diffirent series of lines which constitute altogether 

 the fluorescent spectrum of the element. 



Present theories of the atom usually regard the electrons and 

 other vibrators that are the sources of arc and spark lines as being 

 far within the atom and as affected by external physical conditions 

 only under very special circumstances. Stark believes that these 

 electrons may rotate in circular orbits, the locus of the centers of 

 these orbits being a closed curve, say a circle. This system will 

 be equivalent to a positive or negative charge according to the 

 sense of rotation of these electrons. These electrons we will call 

 ring electrons. Supposing these systems to be positive charges, 

 it will require electrons to neutralize these charges. Several of 

 these neutralizing electrons may be in the outer parts of the atom 

 and under certain conditions might be knocked off from the atom. 

 These easily removable electrons will be called " valency " electrons, 

 and can exist under different conditions of " looseness " of con- 



