( 594 ) 
(ep) =P (y—9)? $e) at 0 
are determined by the equation 
G—p? + Eg + Cary 0, 
6+ ¢#— 2r34 (129) —2pt dp? Hg rs =0, (3) 
or 
These “conspherical points” form on the skew parabola an invo- 
lution of degree six with four dimensions; for, if four of the six 
points of intersection be chosen, the sphere is determined and together 
with it the supplementary pair of points of intersection. From (3) 
follows immediately that six conspherical points are connected by 
the two relations 
= i=0, Baike ee 
6,1 6,2 
between their parametervalues. 
We now prove the following theorems: 
“The spheres determined by the quadruples of points of the skew 
“parabola, conormal with a given point t, intersect this curve still 
“in two fixed points, determined by the equation 
8@—3tt+1=0; 
so they form a net of which these two points are the basepoints. 
And the point 4 describing the curve, these basepoints generate on 
it a quadratic involution of one dimension, of which the two points 
1 
ae Bela are the double points. 
If 7}, To, 73, T, are four points conormal with 4, then according 
to (2) we have the relations 
yy 
= t +t 0, = t+tZ2t=—. . ° e (5) 
4,1 4,2 4,1 3 
If 7, 79, T3, 74 are four points conspherical with t, t3, then 
according to (4) we have 
SY ae aaa St+(_y+h)St+htz,=1 . (6) 
4,2 4,1 
So from (5) and (6) follows immediately : 
1 
to + tg = ty, AI pe a 2st Dg UES Ke MN 
with which is proved what was asserted. For the spheres belonging 
