VETERINARY OPHTHALMOLOGY. 



9 



a double convex lens. (Fig. 5.) Eays of light passing 

 through this are bent toward the perpendicular, and 



Fig. 5. 



Diagram illustrating the composition of a convex lens of a number of 

 plane surfaces. 



therefore these rays come to a focus ; and where the 

 focus is, we will find light and heat, because of the num- 



Fig. 6. 



ber of light and heat rays converged at one spot. Re- 

 member that a ray striking a plane perpendicularly 



