190 Trans. Acad. Sci. of St. Louis. 
draw HF perpendicular to CP, and intersecting CP at K. 
With C as a center and CA as a radius describe a sphere. 
Then from the figure 
Saas p 
tana tana 
Therefore any plane tangent to this sphere, such for ex- 
ample as X, -X,, will cut from the cone a section of the given 
latus rectum. 
Issued May 10,1893. 
