ReRif cation of diverted Figures [Book 1 II. 



eye at Z, will exhibit all thefe points A, L, M, N, 

 &c. within the fpace af, which will in this direction 

 diminifh confiderably the dimenfions of the image, 

 according to the principles already explained in 

 treating of the convex mirror *. The fame will 

 take place with refpect to all the points of the object 

 which are vifible within the lines B Q^G, C R H, 

 D T I, E S K, concentric to the furface of the mirror. 

 Thefe parts muft therefore be very much extended in 

 the drawing or defign, if a perfect image is to be re- 

 prefented in the mirror. Diftorted drawings of this 

 kind are common in the mops of the opticians, which, 

 on -a cylindrical mirror being placed on the board or 

 drawing, difplay perfect figures. The principle of thefe 

 will, however, be very eafily underftood from what has 

 been now ftated. 



The CONICAL MIRROR is reprefented in fig. 6, 

 and this is alfo confidered as a mixed mirror ; for, as 

 well as the cylindrical, it produces at once the effects 

 of a convex and a plane mirror. Suppofe, for inftance, 

 the angle C K F (fig. 7.) to reprefent this mirror, 

 and the lines C K, F K, two of the right lines which 

 compofe it. Thefe two lines would then anfwer to 

 two plane mirrors inclined towards each other, and 

 the rays proceeding from the points A, B, C, falling 

 on the furface at g, b, /, and reflected towards the eye 

 at O, would reprefent thefe points as if at the bafe 

 of the mirror in the oppofite order a, b, c j and the 

 fame obfervation will apply to the points D, E, F, 

 . which are reprefented at d> e, f, as well as all thofe 

 which are in the circles A H D, B I E, C G F. But 



* Viz. by dimimlhing the convergence of rays, and confequently 

 reducing the fize of the image in proportion to the convexity. In 

 the cylindrical mirror, it muft be obferved, that it is !h the breadth 

 nly that this diminution takes place. * 



as 



