the Molecule and Chemical Combination. 537 



powerful method for the study of individual atoms and mole- 

 cules, we shall consider from the point of view of the theory 

 the evidence afforded by this method. 



Let us begin by considering the positively electrified atom. 

 Such an atom is one that has lost one or more of its electrons : 

 but diminishing the number of the electrons round the central 

 charge will increase the stability of those that are left; hence, 

 if we could produce them, atoms which had lost one or more 

 charges would be stable and might be expected to be in 

 evidence in the positive rays. The magnitude of the positive 

 charge cannot be greater, than that produced by removing all 

 $he electrons from the outer ring ; hence we could not have a 

 positive charge of more than 8 units, which is the maximum 

 number of electrons in the outer ring : as a matter of fact, 

 8 is the greatest charge yet observed on any atom in the 

 positive rays. Again, hydrogen has never been observed 

 with more than a single positive charge, which is in agree- 

 ment with the view that its atom contains but one electron. 

 Another way in which the theory might be tested would be 

 to study the positive rays for the vapours of the alkali metals 

 and the alkaline earths : these on our theory contain respec- 

 tively one and two electrons in the outer ring ; hence the 

 vapour of an alkali metal ought not to be able to acquire a 

 double charge, nor that of an alkaline earth a triple one. It 

 is difficult to get these vapours in the positive rays in the 

 ordinary way, but it is hoped that the application of the 

 positive ray methods to anode rays will result in a thorough 

 study of the properties of the atoms of metallic vapours. One 

 result we may deduce already from our observations on the 

 positive rays, and that is that though chlorine is regarded as 

 a monovalent element it contains more than one electron in 

 its outer layer, for chlorine atoms with a double positive charge 

 occur whenever the positive rays pass through chlorine. As 

 chlorine on our view has 7 electrons in its outer layer, it 

 would not be surprising to find chlorine atoms with three or 

 four positive charges. 



Let us now turn to the case of positively electrified 

 molecules. These with one positive charge are to be found 

 in almost every positive ray experiment, though I am not pre- 

 pared to say that every molecule can survive the removal of 

 an electron and acquire a positive charge without dissociating 

 into atoms. 



As an example of the way in which the removal of an 

 electron might dissociate a molecule into atoms, Ave may 

 take the case of: a molecule of chlorine in which the two cells 

 are supposed to have only two electrons in common ; if one 



