Physics. — “On the rings of connecting-electrons in Braaa’s model 
of the diamonderystal” By D. Coster. (Communicated by 
Prof. H. A. Lorentz). 
(Communicated at the meeting of October 25, 1919). 
The beautiful investigations of the two Braces‘) have given us 
a clear insight in the structure of the diamonderystal. As is known 
according to these investigators the structure of this crystal may be 
represented by the following scheme: a set of cubes, where the C- 
atoms are situated in the corners and in the centres of the side- 
planes; in which another set of identical cubes, which may be 
obtained from the first by translating it parallel to itself in the 
direction of one of the cube-diagonals over a quarter of this diagonal 
(see fig. 1, where only those atoms are represented, which are 
situated within a fundamental cube). If we assume, that the valency 
of the atoms also have a principal meaning in the crystal, this system 
is of a perfect symmetry. Every C-atom namely has in its neigh- 
bourhood four other atoms at the same distance and symmetrically 
situated. (The lines which join each atom with its + neighbour- 
atoms form the diagonals of a cube). In this way the four valencies 
of the C-atoms are satisfied. Now we may assume, that the “bonds” 
between the atoms are formed by rings of electrons as it is the 
case in Bour’s model of the hydrogen-molecule. DrByx and SCHERRER °) 
for instance suggest a model, where each carbon-atom sbould part 
with four electrons, one for each valency, for which consequently 
two electrons should be available. These should revolve about the 
connecting-axis of two nuclei in a plane perpendicular to this axis 
and half-way the distance between the nuclei. So the nucleus itself 
should still retain two electrons and behave at a distance as a four- 
fold charge. If once we have admitted, that the “bonds” are formed 
by rings of electrons, from the point of view of symmetry there is 
much to be said in favour of this model’). 
Degije and ScHERRER however arrive at the conclusion, that such 
a model is inconsistent with the experimental data of the two 
1) Proc. Roy. Soc. Londen (1914) A 89, p. 277. 
See also: Brace. X-rays and crystalstructure. 
2) Phys. Z. S. (1918) XIX, p. 476. 
8) Of course many difficulties yet remain, e.g.: how is the direction of rotation 
in the orbits. We can also say but little about form and magnitude of the orbit. 
