( 754 ) 
The domains of the plane occupied by these different kinds of 
curves are bounded by the curves which correspond to 4 = C, and 
eG 
For these values of / a degeneration takes place. 
For %—'U, in? 
C= G, and VEC. = cos Pp = — o's eRe 
The latter curve lies on the left of OU, it begins and ends in the 
; a 
noe. Gb Pe 
») 
For t= C, in: 
$= C, and V5(E — C,) cosy =o'VC, —S. 
The latter curve lies on the right of O; it commences and ends 
: i ds Tt 
bn ihe points: bbp dt 
9 
To investigate how the system of curves varies when 9’ is changed, 
it is sufficient to investigate the variation of the degenerated curves. 
The result is, that the domain of the curves surrounding O is very | 
small for small values of 0’ and it extends according as 9’ 
increases, so that those curves are most important for great values 
of o’. 
So we have for small values of 09’ by preference the case, that p 
moves to and fro between two extreme opposite values, for great 
values of 0’ by preference the case that assumes all values. 
Furthermore we notice that according as 9’ increases the curves 
surrounding (} as centre, 1. 0. W. s and on account of this the e@’s 
vary but little. We thus approach the general case where y’ has 
become so great, that we can no longer speak of a relation. 
Here too we get for each value of 9’ for the maximal and minimal 
value of & an isolated point on the axis of the angles. 
Fig. 6 gives some curves for a rather small value of 9’, fig. 7 for 
a rather great value of 9’; the —-— lines indicate the degenerated 
curves. 
RELATIONS BETWEEN 3 OF THE FREQUENCIES OF VIBRATION FOR 
WHICH J ===. 
§ 17. Two of these relations have to be discussed, namely: 
(A) n, + 2n, —n, = 9, 
(B) —n, + 2n, —n, = 09. 
We commence with the determination of the disturbing terms of 
the second kind in the equations of motion. These contain no 
