S04« optics. 



tions, to the eye f, at the end of the small tube tt, 

 which is joined to the great one. 



Let us then suppose the object A B to be at such 

 a distance, that the rays C y flow from its lower 

 extremity B, and the rays £ from its upper ex- 

 tremity A. Then the rays C, falling parallel upon 

 the great mirror at D, will be thence reflected, by 

 converging in the direction D G ; and by crossing 

 at I in the principal focus of the mirror, they will 

 form the upper extremity I, of the inverted image 

 I K, similar to the lower extremity B of the object, 

 A B : and passing on the concave mirror L, (whose 

 focus is at 7i) they will fall upon it at g 9 and be 

 thence reflected converging, in the direction g N, 

 because g m is longer than g n ; and passing 

 through the hole P in the large mirror, they would 

 meet somewhere about r, and form the lower ex- 

 tremity d of the erect image a d, similar to the 

 lower extremity B of the object A B. But by pass- 

 ing through the plano-convex glass R in their way, 

 they form that extremity of the image at b. In 

 like manner the rays E, which come from the top 

 of the object A B, and fall parallel upon the great 

 mirror at F, are thence reflected converging to its 

 focus, where they form the lower extremity K of 

 the inverted image I K, similar to the upper ex- 

 tremity A of the object, A B ; and passing on to 

 the small mirror L, and falling upon it at h, they 

 are thence reflected in the converging state h O ; 

 and going on through the hole P of the great 

 mirror, they would meet somewhere about q, and 

 form there the upper extremity a of the erect 

 image, a d, similar to the upper extremity A of the 

 object, A B ; but by passing through the convex 

 glass II in their way, they meet and cross sooner, 



