[BAKErR] CORRELATION OF CURVE OF THE SECOND ORDER 33 
Then retaining u as a base line, let A A, or ul, be the other. Also B, 
and C, being the new radiant points, S C or u!, is the new perspective 
axis. 
Hence, given a point D on u, we construct at once the corresponding 
point D! on ul, and the new ray D D' is reached. 
But this ray D D’, is the same as the preceding D D,. For the 
triangles P S S, and S' P' §*, are such that the lines joining correspond- 
ing points P and §', Sand P', S, and S,’, pass through the same point 
C. Hence the intersections of corresponding sides P Sand S’ P', S 8, 
and P! §}, S, P and S; S’, i.e., the points D, D; and D,, all lie on the 
same straight line. That is the new rays D D,and D D,' are identical 
And from this point the proof proceeds as in the preceding demonstration. 
Sec. III., 1902. 3. 
