72 MIRRORS. I 



on the inside, is sometimes suspended from the ceiling of a " 

 room. It affords a sort of panoramic view of surrounding \ 

 objects, though not ail in natural proportion of size. When : 

 a convex mirror can be placed before a window^, either with i 

 a good prospect, or where there are a number of persons^ 

 passing and repassing in their different employments, the ^ 

 images reflected from it will be erect, and behind thei 

 surface ; and a landscape or a busy scene delineated on one ' 

 of them is always a beautiful object to the eye. Concaved 

 mirrors make objects appear larger, but distorted. If one be ' 

 hung on the wall of a room, or fixed in a chair, a person be- j 

 yond the focus sees his image inverted. As he puts forward f 

 his hand the image in the glass appears to do the same, as j 

 if to shake hands. As he tries to clasp the hand it vanishes' 

 from his view. Let the spectator hold out a knife in hia-' 

 hand, the image will appear to do the same ; and so strong ; 

 will be the impression on his mind, that he will feel a reluc- l 

 tance to run his hand forward against the apparent weapon. ) 

 A concave mirror throws back the sun's rays into one point ^ 

 or focus, where paper or gunpowder may be set on fire. ] 

 Mirrors are sometimes made of a cylindrical concave form , 

 and as one of them is placed either upright or on its side, 1 

 the image of the picture is distorted into a very long or a I 

 very broad image. Reflecting surfaces may be made of i 

 various shapes, and if a regular figure be placed before an ^ 

 irregular reflector, the image will be deformed ; but if an .^ 

 object, as a picture, be painted deformed, according to cer- i 

 tain rules, the image will appear regular. Such figures and | 

 reflectors are sold by opticians, and they serve to astonish | 

 those who are ignorant of these subjects. i 



Small convex reflectors are made for the use of travellers, -] 

 who, when fatigued by stretching the eye to Alps towering 

 on Alps, can by their mirror, bring these sublime objects 

 into a narrow compass, and gratify the sight by pictures i 

 which the art of man in vain attempts to imitate. ] 



Questions. — 1. What are the three kinds of mirrors? 2. How 

 do convex mirrors make objects appear ? — concave ? 3. What are 1 

 .some of the experiments that may be performed with them ? 4. How \ 

 do cylindrical concave mirrors make an image of a picture appear? l 

 [Note. A mirror is sometimes called a Spoc'ulum, pi. Spec'ala.] 5. 1 

 Describe fig. 27, 



