12 Mr. W. Sutherland on the 



dental that this 4'46 is exactly double the 2*23 calculated 

 just above in connexion with C. It appears then that the 

 electric moment o£ a constitutive electron pair in the 

 atoms o£ the Be family is 1*64 times that of those o£ the Li 

 family. 



When we proceed to develop for the non-metals formulas 

 like (5) and (6) we find complete similarity in principle, but 

 a most instructive contrast in detail. In the case of the 

 atoms of the metals in their compounds we found that ex- 

 ternal electric intensity acts first upon the special pair of 

 electrons, and through these upon the constitutive electrons. 

 In the atoms of non-metals, on the other hand, we shall see 

 immediately that an external electric intensity acts first upon 

 the constitutive electrons, and through these upon the special 

 pair of electrons. The most marked electric distinction 

 between the atoms of metals and non-metals, both in the 

 combined state, is that es in the metals is proportional to a, 

 and in the non-metals to a 3 . It appears that in the atom of 

 metal the special pair of electrons separating from one another 

 to a distance proportional to a control the whole electric 

 moment of the atom so that it is proportional to a. But in 

 the atom of non-metal, on the other hand, as es is propor- 

 tional to a 3 , the intensity of electrization £s/(47ra 3 /3) is 

 constant, a result which makes it appear that in the atom of 

 non-metal the pairs of constitutive electrons are so arranged 

 that they dominate the special electron pair, and make the 

 average intensity of electrization uniform in an atom and 

 nearly constant from the atom of one non-metal to that of 

 another. We shall proceed, therefore, on the assumption that 

 in order to reach the special pair of electrons with an external 

 electric intensity F we must first act upon the n pairs of 

 constitutive electrons. To find the electric moment imparted 

 by F to one of these we need only replace in our calculation 

 for the moment imparted to er in an atom of metal er by ea-, 

 and R by a/n 11 ' 3 and W by w, obtaining 3e 2 Fa/4:7r(a/n l/S ) 2 w. 

 In the atom of metal I was led to use a where a/n l l 3 occurs 

 here, an important difference. The electric intensity due to 

 n such moments in the atom is W = 2>ne 2 ¥aj^.ir(ajn l ' 3 y 2 wa z . 

 Under this the whole atom is strained so that its moment 

 es is given in the direction of F an electric moment 

 3e 2 F's/47ra 2 W, with which is associated the electric intensity 

 F'^a^FVlTT^Wa 3 . 



It is important to notice the " dimensions " of this intensity. 

 If W = 27r^V/3(2a) 6 and es is proportional to a 3 , the co- 

 efficient of F' is of dimensions —2 in a. It will appear 

 immediately that in each natural family of the non-metals, 



