PROFESSOR CATLEY ON CERIC SURFACES. 
275 
Section Y=12-B 4 . 
Equation WXZ+(X+Z)(Y 2 -aX 2 -5Z 2 )=0. Article Nos. 85 to 94. 
85. The diagram of the lines and planes is 
11 '. 22 ' 
12 '. 21 ' 
2x12=24 
2x1= 2 
9 45 
Biplanes containing 
rays 1, 2 and 1', 2 ' 
respectively. 
Plane touching along 
edge and containing 
the transversal. 
Biradial planes each 
containing a ray of 
the one and a ray of 
the other biplane. 
Planes each through 
the transversal. 
86. The planes are 
x=o, 
[12] 
z=o, 
[1'2'] 
x+z=o, 
[0] 
— XyZ ft-)- Y — Z-yZ$— 0, 
[11] 
X-yZ fl. -|-Y — Z</6 = 0, 
[12] 
— - XyZ CL- {-Y-{-Z.yZ$ = 0, 
[21] 
XyZ ®-j- Y-j-ZyZ ^ = 0, 
[22] 
^Cx+z)+w=o, 
[11' . 22] 
—2 y/«T(X+Z)+W=0, 
2 p 2 
[12' . 21]. 
