MAGNIFYING GLASSES. 
1. Magnifiers intermediate between spectacle-glasses and microscopes. —2. 
Variously mounted.— 3. Extensive use in the arts.—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 Superseded nevertheless by the improvement of compound micro¬ 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. Coddington 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 
Lardker’s Museum of Science. h 97 
No. 94. 
