COMMON THINGS THE LOOKING-GLASS. 



On emerging from the anterior surface of the glass, the ray is 

 again refracted, taking the direction o E', which makes with o o' 



Fig. 4. 



the same obtnse angle as s o made with o o'. The eye placed at 

 E', therefore receiving the ray of light in the direction o E', sees 

 the object s as if it were at s'. 



14. The light in passing through the glass from o to o', and 

 from 0' to o, loses more or less by the absorption of the glass. A 

 small part also is lost by imperfect reflection, at o', and again in 

 emerging from the anterior surface, a small portion of the light 

 is reflected back through the glass. 



From these causes, the image seen at s' is a little more faint 

 than the object s, of which it is the reflection. But the image s, 

 produced by the reflection of the anterior surface, is incomparably 

 more faint. 



15. The line s' s, which joins the two images being at right 

 angles to the surfaces of the glass, will be viewed more and more 

 obliquely, the less oblique the line of vision E o is to the glass, and 



126 



