A GEOMETRICAL CONSTRUCTION FOR FIND- 
ING THE FOCI OF THE SECTIONS OF A 
CONE OF REVOLUTION.* 
Epmunp A. ENGLER. 
Fig. 1 represents a meridian section of a cone of revolution. 
S is the vertex, and SC, is the axis of the cone; SD, and 
SD, are the elements cut from the cone by the plane of the 
FIGURE 1. 
meridian section; Z,Z, represents a plane perpendicular to 
the meridian meaticns C, and C, are the centers of shinee: : 
oy ert pave or aaa 
before The Academy t. Lonis, March 21 
