CONTENTS 
*** As this book is not paged , the figures in the Table of Contents refer to 
Paragraphs , and not to Pages. 
OPTICAL 
Chap. I.—1. Great importance of the 
subject in relation to all the effects 
of vision.—2. Explanation of how 
an object is seen with the naked eye. 
—3. Images produced by plane re¬ 
flectors.—4. How rays are reflected 
from such surfaces.—5. Experimen¬ 
tal verifications of this.—6. Image 
of a point in a plane reflecting sur¬ 
face.—7. Image of an object in the 
same.—8. Realand imaginary images. 
•—9. Images produced by spherical 
reflectors. —10. By a concave re¬ 
flector.—11. Experimental verifica¬ 
tion.—12. Variation of position, and 
magnitude of image.—13. Images 
in convex reflectors.—14. Images 
produced by transparent bodies.— 
15. Refraction.—16. Cases in which 
light will not enter a transparent 
body.—17. Reflection of objects in 
water.—18. The fallacy of the fable 
of ‘‘the Dog and the Shadow.’’— 
19. Objects seen at the bottom of a 
transparent body. — 20. Case of 
water and glass.—21. Broken ap¬ 
pearance of a rod immersed in water. 
—22. Cases in which rays cannot 
emerge from a transparent body.— 
23. Experimental verification.—24. 
Reflection by a rectangular Prism.— 
25. Images produced by lenses.— 
26. Six kinds of lenses.—27. The 
axis of a lens.—28. Example of 
each kind of lens. —29. Optical image 
produced by a convex lens.—30. Re¬ 
lative position of the object and image. 
IMAGES. 
Chap. II. — 31. Experimental verifica¬ 
tion.—32. Variation of the magni¬ 
tude of the image.—33. Principal 
focus and focal length.—34. Varia¬ 
tion of position, and magnitude of 
image.—35. When images real, and 
when imaginary.—36. Images pro¬ 
duced by concave lenses.—37. Focal 
length varies with refracting power. 
—38. Refracting power depends on 
material of lens. — 39. Spherical 
aberration. — 40. Images produced 
by lenses not absolutely clear and 
distinct.—41. Series of images.— 
42. Nebulous and confused effect. 
—43. Spherical aberration greater 
near the borders. — 44. Increases 
with the curvature.—45. And with 
the magnifying power.—46. Sphe¬ 
rical distortion.—47. Curved images. 
■—48. How to diminish spherical 
aberration.—49. Lenses made from 
diamonds and other precious stones. 
—50. Ineffectual attempts at im¬ 
provement by this means. — 51. 
Methods of diminishing spherical 
aberration by proper adaptation of 
curvatures.—52. Aplanatic lenses* 
—53. Chromatic aberration.—54. 
White light compound.—55. Co¬ 
loured lights sometimes compound. 
56. Images produced by homogeneous 
lights.—57. Images produced by 
compound light.—58. Lenses always 
produce several images of a natural 
object.—59. Why they are not al¬ 
ways so confused as to be useless for 
