1274 
The set of values (5) satisfies (6). 
In this way we have shown the maximum to lie really in the 
direction of reflection. We can see this without calculation, and I 
principally gave the above calculation to show the connection between 
].avE’s considerations and mine. 
For if P the origin of rays, and £ the point of observation, both 
are situated at a distance from the molecules of a plane which is 
infinite with respect to the dimensions of the plane of which A and 
B are arbitrary molecules, then the way PAL = PBL, and there 
is interference of the light emitted by the molecules, if the angles of PA 
and AL with the normal of the plane are equal. Thus there is 
interference in ZL, if the point lies in the direction of the ray 
reflected in the plane. For the rest the disturbance of equilibrium, 
if N is the number of particles of the plane, will be N times as 
great as the disturbance caused by one particle, and therefore the 
intensity will be N° times as great. 
The intensity of the maximum is of the order of the number of 
molecules in a plane, i.e therefore, of the order of the “two-cone” 
maxima of Laue. As we may now presume, all pulses will interfere 
in the same direction which originate from planes in the crystal 
parallel to the one considered. The equation of similar planes is 
aa + by JS E80 
where I must be a whole number, xyz being whole multiples of the 
side a, the coefficients a, b, and c also being whole numbers. 
Expressed in «37 the equation takes the form 
a2(l—a)-yBP—2y =d. 
We therefore have 
a b C 8a 
= = == 
lek Pay Up ae 
which gives for «py the same values as in the preceding formula, 
whereas we have 
2a 
== sa 
a? + b? -- Ea 
or 
Ds dd: 
EN 
It is easy to introduce into this formula the smallest distance of 
. . a hl . 
the planes under consideration. It amounts to For mt 
Va? + $?4- ¢? 
a \k, (La) — k, 8—£, Yi 
