1905.] on the Structure oj the. Atom. 63 



Le Bel on the asymmetric carbon atom, which supposes that the 

 attractions exerted by a carbon atom are exerted in certain definite 

 directions, these directions being such that, if the carbon atom is at the 

 centre of a regular tetrahedron, the attractions are along tlie lines drawn 

 from the centre to the corners, will perceive the reseinljlance between 

 that theory and the results we have been discussing. There is, 

 however, an important difference between the two, for on our theory 

 the forces exerted by the atom are not confined to any special direction ; 

 the atom exerts forces all round. It is only, however, in certain 

 directions that these forces can keep a second atom in stable equilibrium. 

 We picture, then, the atom A as being connected with a limited numl^er 

 of closed regions of finite size, and any body attached to the atom 

 must be situated in one of these regions ; when each of these regions is 

 occupied by another atom, the atom A can hold no more bound to it, 

 and is said to be saturated. 



I have not time this evening to discuss in any detail further de- 

 velopments of these ideas. I may however, in conclusion, call atten- 

 tion to a point which is illustrated by the behaviour of the carbon 

 compounds. Suppose that C^ C2 are two carbon atoms near together. 

 Then when 



Ci a /? C2 



both atoms are present, regions a, ^ near the line joining Cj C2, which 

 were valency regions for C^ and C2 when these atoms were alone, 

 may cease to be valency regions when both are present. For take the 

 case when the stability is due to the magnetic force produced by the 

 rotation of the corpuscles within the atoms. Along the line C^ C2, the 

 magnetic force due to C^ and C2 will be in opposite directions, and in 

 the region near the middle of C^ C2 the resultant magnetic force 

 would be very small, so that in this the equilibrium of a charged 

 body would be unstable ; thus a y8 would cease to be valency regions. 

 This reasoning would not apply to the valency regions of C^ on the 

 side opposite to C2, nor of those of C2 on the side away from Cj, so 

 that six valency regions would remain. Thus if we consider the 

 tetrahedra formed by the valency regions round our carbon atoms, 

 then if two carbon atoms are placed so that two vertices of these tetra- 

 hedra come together, the regions near these vertices will cease to be 

 valency regions, and the compound formed would have to be of the 



type H — yC Cv- — H, the two carbon atoms being held together by 



forces of the M type. If the tetrahedra were placed so that two edges 

 of the tetrahedra came together, we could show similarly that the four 

 valency regions at the ends of the edge would be suppressed and the 



compound would be of the type, tt^C C<^tt, while if two faces of 



the tetrahedra came together the valency regions in these faces would 

 be suppressed, and the compound would be of the type H — C C — H. 



