Fig. 1. 



COMMON THINGS. 



THE LOOKING-GLASS. 



1. Though common and familiar, little understood. 2. Image of an 

 object produced by it vertically erect, but laterally inverted. 3. 

 Image of an object parallel to the looking-glass. 4. Image of an 

 object inclined to the reflector. 5. Series of images formed by two 

 reflectors. 6. Example in rooms furnished with several mirrors. 

 7. Reflection by a looking-glass takes place at the posterior surface 

 silvering. 8. Analysis of the effect of a looking-glass upon the 

 light falling on it. 9. Conditions on which the goodness of a looking- 

 glass depends. 10. Effect of mirrors flush with the floor. 11. Best 

 method of cleaning mirrors. 12. Light reflected from the silvered 

 surface. 13. How a double image is produced. 14. Why one image 

 is much more faint than the other. 15. Positions in which the -two 

 images are visible. 16. The image usually seen produced by the 

 posterior surface. 17. Effect of light absorbed by the glass. 

 18. Glasses rendered unfaithful in their tints. 19. A good glass 

 must have its surface parallel. 20. Defects of low-priced glasses. 



1. How common and familiar in all countries, and all houses 

 from the palace to the cottage is that useful and beautiful article 

 the looking-glass. Its fragments presented to savages are prized 

 above gold, excite their wildest admiration and unbounded 

 astonishment ; its uses and its abuses have, in all times, supplied 

 a theme to the moralist, a figure to the orator, a metaphor to the 

 poet, and fanciful allusions without number to the dramatist. 



Since a very small proportion of the millions who place 

 themselves daily before the looking-glass, and profit by its silent, 

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