EXPERIMENT AT THE WINDOW. 123 



jects through a glass, we do not see those reflected in it, 

 because the light shining on the objects beyond that are 

 seen through the glass is usually sufficient to overpower, 

 or nearly overpower, the reflected light ; but, by throwing 

 a very strong light upon any object that is to be reflected, 

 we can remedy this, and enable ourselves to see the image 

 of the illuminated object by reflection as plainly as we do 

 those beyond the glass directly, as can be shown in a very 

 simple and conclusive manner by the experiment ah'eady 

 explained of holding a piece of paper, with a lamp or can- 

 dle shining directly upon it, near a pane of glass in the 

 window in the daytime. The paper thus illuminated will 

 be very distinctly seen reflected in the glass. Indeed, 

 white paper emits usually so much light that it can ordi- 

 narily be seen faintly reflected m the glass, if it is held 

 near, without any artificial illumination ; but the bright- 

 ness of the image will be greatly increased by the bright- 

 ness of the light shining upon it. 



On the same principle, if you stand near a window, with 

 your back toward it, and hold up a pane of glass, or any 

 small piece of glass, before your eyes, you will see the ob- 

 jects out of doors very plainly reflected in it, especially if 

 it is a bright day. You can also see through the glass the 

 objects that are in the room, but the objects outside will 

 be seen too, very distinctly, and the more distinctly in pro- 

 portion to the brightness of the light which shines upon 

 them. 



Thus, when for any reason we wish to see any object dis- 

 tinctly by reflected light in a glass which is not silvered, we 

 require a very bright light to shine upon it, and this is con- 

 sequently one of the purposes for which a very bright light 

 is required. 



On what principle and by what methods these very bright 

 lights are obtained will appear in the next chapters. 



