1901-2.] Prof. Chrystal on Trisector and Quartic Trisedrix. 17 
On the Relation of Miller’s Trisector to the Quartic 
Trisectrix, with a Description of a Seven-bar Lima- 
conograph. By Professor Chrystal. 
(Read November 18, 1901.) 
If, instead of causing the point B of the trisector to move along 
an arm of the angle, we cause P, the intersection of the two edges, 
to move along an arm, and find the locus of the point B, we get 
another curve associated with the instrument. 
If 0 X (fig. 4) be the fixed arm, O being the fixed pivot of the 
trisector, 0 A = A B = a, say, and the angle B P X (4 0) be twice the 
PROC. ROY. SOC. EDIN. — VOL. XXIV. 2 
