AND ON THE CONSTRUCTION OF A DOUBLE-SIXER. 
381 
521] 
Point 5 by means of the conic 23ol'4 / 6 , . 
The conic is 
Fx + Gy + H = l -=-t, (2,3) 
where 
Fc. +H = ~, (4') 
c 
Fm 1 +G^/M 1 + H= 1 —(6') 
m 1 
Fm - G *JM + H = i—^, (l 7 ). 
m 
Everything is the same as for the point 4 except that b, c are interchanged: 
hence writing Q instead of P, and using A, B, G to denote as before, we have 
abc F = — a — b + Q, 
*JMdbc G = (m — c) (— to + Q)> 
abc H = ab + ac + be — cQ, 
and 
and 
(f> — a 
C> (ib-a) 
B 2 
, 4 (to — a) (m — b) (m — c) (c — 6) (a — 5) 
■*>-»= ^ - 
ri 2 (b — c) 
<£ — c = 
P 2 
Q-5 _ 2 O~fr)( m ~ c )0~&) 
A (m — b) 
P 
, 2 (m— b) (m — c) G (a — b) 
= # > 
V<1> = 2 Vif (c — 6) (6 — a) 
ps 5 
which determine <£, V4>. 
Point 3' by means of the conic 1263'4'5'. 
The conic is 
(x — b)(x — c) 
Fx + Gy + H — 
V 
(*', 5')