1281 
points, that is to say there are three y* which have a six-point 
contact with a conic in 5. 
From this it ensues that the locus 6 of the sertactic points N is 
intersected by any ray s from A in 3 points, and has triple points 
in the five base-points 45. Between the plane pencil (s) and the 
pencil (p°) exists therefore a (3,3); for any g* bears three points S. 
Consequently the “sertactic” Curve o is of order twelve. It has 
a nonuple point in A, and triple points in the five single base-points. 
Symbol o1? (4°,5B®). 
Other singular points it cannot have for in genus it must answer 
to tf; for to each point of inflexion I belongs one point S and the reverse. 
$ 6. A conie touching p° in Bin five points, intersects it moreover 
in a point Rk, which I shall call the residual point of B. The locus 
e of the points A has a quintuple point in B; the tangents fall 
along the tangents of the three conics, which have a six-point 
contact in B, and along the two stationary tangents of the two g°, 
which have their point of contact in 5. 
The straight line LR intersects the corresponding curve g* in 
the second tangential point 5"). Now the eurve r? has in Ba node, 
DI 
in Ca triple point; on BC therefore lie moreover four points B", 
so that @ must pass four times through C. As B" further comes 
thrice in C three points PR lie on BC; but o is then a curve of 
order twelve. Of its intersections with an arbitrary yg’ 5 lie in B, 
16 in the points C, one in the residual point of B; we conclude 
from this that 9 has a septuple point in A. 
We can represent it therefore by the symbol 9'%(A’,4°,4C")?). It 
may serve as confirmation that the curve must be rational. 
Physics. — ‘further experiments on the moment of momentum 
existing in a magnet’. By Dr. W. J. pr Haas. (Communicated 
by Prof. H. A. Lorentz). 
(Communicated in the meeting of September 25, 1915). 
Introduction. In a former paper on this subject *) it has been 
remarked that the attempt to determine the sign of the effect had 
proved a failure. New experiments were therefore desirable. But 
!) Cf. e.g. SALMON-FIEDLER, ibid. 
*) In my paper referred to ahove (Arch. Teyler) 1 have considered the curve 
p for a general pencil (om); any conic associates then to a point of contact 
B (2m—5) residual points R It has the symbol ,10m+2(B15, C10) 
For the sextactic curve the symbol ¢247”—27 (B12) was found there. 
3) A. Ewsrem and W. J. pe Haas, These Proceedings, XVIII p. 696, 1915. 
