at the total solar Eclipse in 1882 



349 



principle involved is that the angles at which rays strike 

 and are reflected from a mirror surface are equal. The con- 

 struction is shown in the diagram Fig. 5. On the straight 



Fig- 5- Geometrical Construction of Reflector used. 



line OP, which represents the axis of the instrument, lay off 

 the length AB=2 inches; this is the focal line. Through 

 A and at right angles to AB draw Ax, and on it make 



