1 20 Rtfleflor Half the Size of the ObjeH. [Book III. 



jcct, cuts the right line o h E, at E. Let B i be a ray 

 of light proceeding from the foot of the object at B 

 to the mfrror at /, and n i a perpendicular to the mir- 

 r.or from the point /', where the ray B / falls upon it ; 

 this ray will be reflected in the line i o, making an 

 angle n i 0,, equal to the angle B in, with that perpen- 

 dicular, and entering the eye at o : then will the foot 

 F of the image appear in the direction of the reflected 

 ray oi, produced to F, where the right line BF cuts 

 die reflected ray produced to F. All the other rays 

 that flow from the intermediate points of the object 

 A B, and fall upon the mirror between b and i, will 

 be reflected to the eye at o ; and all the interme- 

 diate points of the image E F will appear to the 

 eye in the direction of thefe reflected rays produced. 

 But all the rays that flow from the object, and fall 

 upon the mirror above h y will be reflected back above 

 the eye at o j and all the rays that flow from the ob- 

 ject, and fall upon the mirror below /, will be re- 

 flected back below the eye at o : fo that none of the 

 r r iys that fall above , or below i, can be reflected to 

 the eye at o ; and the diftance between h and / is 

 equal to half the length of the object A B, if the cye^ 

 or o, is in the line A B produced : for then A b will 

 be equal to k 0, and A h is equal to b E. Therefore 

 Jj E is equal to o h, and o b is one half of o E 3 and 

 confequently i b (from fimilar triangles) is equal to 

 one half of E F or A B. 



In rooms where looking-glafles are placed parallel 

 and oppofite to each other, a perfon looking into one 

 fees feveral images of himfelf , for rays will be re- 

 flected from one glafs to the other, and each image 

 becomes an object to the other glafs. If, inftead of 

 be'.ng parallel, the glafles were placed oppofite to each 

 other,, but making an acute angle, there will be fe- 



veral 



