354 



a solar Calorimeter used in Egypt 



Join B^B Z ; then B^B Z is the line which represents in section 

 the innermost mirror. 



Fig. 6. Geometrical Construction of Reflector, when the position of a point on 

 one of the mirrors, and the position and length of the focal line, are given. 



Through 2 draw a straight line O 2 P 2 parallel to OP, and 

 on it lay off the length B^A 2 = BA. 



