L 
Vili 
CONTENTS. 
215—218. Radii of curvature of oblique and normal sections. •. 184 
219—226. Normal Sections of greatest and least curvature... 189 
227—229. Intersection of consecutive normals of a surface... 197 
230—23?. Lines of curvature, Principal radii of curvature, and 
umbilici of surfaces 200 
APPENDIX. 
Problems. 
209 
Students reading this subject for the first time may confine their 
attention to the following Articles. 
1—41, 42—52, 57—71, 79—84, 107, 109—115, 121—126, 131. 
ERRATA. 
PAGE 
EINE 
ERROR. 
CORRECTION. 
10 
3 
yz 
xz 
21 
22 
before this assertion supply the converse of 
109 
15 
X, y, z 
h, k, l 
118 
1 
xy 
xz 
121 
9 
+ 7 s + 38 
+ 25 s - 9 
so that the surface is 
an ellipsoid. 
133 
12 
2 A\x 
2 A\x' 
136 
(PQ .V 
1 /PQ \* 
5 
~br +1 ) 
64 ( D +1 / 
191 
last line 
A h tan 3 6 
* ax 
i dr h 
3 dx ' 
205 
24 
+ 4 uv 
+ ip 2 q 2 uv 
which causes the two succeeding equations 
equation at the top of p. 206 should be 
to be incorrect ; the 
|(l+/) 2 )0 
-(l + 9 S - 
2p*q*\ „ , (l+p 2 )(l+ 9 2 )-pV.. , , , „ 
- Up) u 5 (1+J»*y 4m W-0. 
231 
1 
(rr'r" 2 ) 
(rr'r") 2 
251 
1 
z u 
z n