Fig. 15. SIMPLE MICROSCOPE. 



MAGNIFYING GLASSES. 



1. Magnifiers intermediate between spectacle-glasses and microscopes. 2. 

 Variously mounted. 3. Extensive use in the aits. 4. Their magni- 

 fying power explained. 5. Visual magnitude. 6. Standard of visual 

 magnitude. 7. Distance of most distinct vision. 8. Visual magni- 

 tude at ten-inch distance. 9. Magnifying power of a convex lens. 

 10. Effect of the same lens with different eyes. 11. Superficial and 

 cubical magnifying power. 12. The eye to be placed close to the 

 lens. 13. Magnifying power depends on focal length. 14. Focal 

 length depends on convexity and materials of lens. 15. Lenses of 

 different materials. 16. Spherical aberration less with a greater 

 refracting material. 17. Diamond lens. 18. Magnitude of lens 

 greater with more refracting material. 19. Advantages of gem lenses. 

 20. Superseded nevertheless by the improvement of compound micro- 

 scopes. 21. Magnifiers for reading. 22. For miniature-painters and 

 engravers. 23. For watch-makers, jewellers, &c. 24. Supports for 

 these. 25. Pocket magnifiers. 26. Coddingtou lens. 27. Doublets. 

 28. Their optical effects. 29. Their advantages over single lenses. 

 30. Method of mounting them ; triplets. 31. Mounting of hand- 

 doublets. 32. Method of mounting doublets of high power for dissec- 

 tion and similar purposes. 



1. MAGNIFYING glasses hold an intermediate place between the 

 spectacle glasses, used by weak-sighted persons, and the micro- 

 scope ; and when they possess considerable magnifying power, they 



LARDNER'S MUSEUM OF SCIENCE. H 97 



No. P4. 



