1639 
Dh. a c,, which has degenerated into a straight line passing through 
two of the base-points and a conic passing through the u —2 remain- 
ing ones. 
Noe oe) BO 
; 2.1 2.1 
c. a ¢,, Which has degenerated into a straight line passing through 
one of the base-points and a conic passing through the g—1 
remaining ones. 
Number n—2 for each base-point. Total amount (9—n) (n—2). 
d. a c,, which has degenerated into a straight line passing through 
none of the base-points and a conic passing through « base-points. 
(n- 
Number ————-——. 
The total amount therefore is 380—n, corresponding to 80—n 
bitangents of the plane intersection of ®'7, and on account of the 
supposed difference of the base-points those of the @ case give rise 
to (9—n) (8—n) of the 1st class, those of 6 to +(9—n) (8—n) of the 
dst class, those of c to (9—mn) of the (n—2)rd class, those of d to 
(n—2) (n—3) 
2.1 
one of the class 
6. For each of these the order is to be determined now. In the 
a case, the part of the degenerate intersection, represented in the 
plane by a base-point, has one free intersection with any surface 
of S,. Such a curve can only occur as part of a degenerate curve 
of intersection of two surfaces of a net determined by the 7 points 
P,,..., Py, if it passes through one of these points and consequently 
has no free intersection any more with a surface of the net of 
surfaces. 
This, however, leads to an impossibility as in that case a surface 
is always to be obtained passing through two curves of the same 
kind, which does not oceur. 
In the 4 case the same is the case for the parts represented by 
the straight line. 
For c, the curve, represented by the straight line, has two free 
intersections with any surface, and is only to be taken as part of 
a degenerate intersection, if it passes through two of the points 
nest 
That this is also impossible ensues from the fact that on a surface 
no two equal curves (represented as a straight line passing through 
two points) will intersect in a point. 
