2. (Pg. 169) Why do objects of the same size appear smaller when distant, than when near? 3. (Pg. 169) Why do not two objects, known to be equal in size, appear to differ, when at different distances from the eye? 4. (Pg. 169) How is this exemplified, by a house seen through a window? 5. (Pg. 170) Why do rows of trees, forming an avenue, appear to approach as they recede from the eye, until they eventually seem to meet? 6. (Pg. 170) In drawing a view from nature, what do we copy? 7. (Pg. 170) What is the difference in sculpture, in this respect? 8. (Pg. 170) Excepting the rays from an object enter the eye, under a certain angle, they cannot be seen; what must this angle exceed? 9. (Pg. 170) What two circumstances may cause the angle to be so small, as not to produce vision? 10. (Pg. 170) Motion may be so slow as to become imperceptible, what is said on this point? 11. (Pg. 170) Under what circumstances may a body, moving with great rapidity, appear to be at rest? 12. (Pg. 170) Upon what does the real velocity of a body, depend? 13. (Pg. 171) What must be known, to enable us to ascertain the real space contained in a degree? 14. (Pg. 171) What is explained by fig. 2, plate 17? 15. (Pg. 171) What is said respecting the evidence afforded by our senses, and how do we correct the errors into which they would lead us? 16. (Pg. 171) An image of a visible object is formed upon the retina of each eye, why, therefore, are not objects seen double? 17. (Pg. 172) By what experiment can you prove that a separate image of an object is formed in each eye? 18. (Pg. 172) Under what circumstances are objects seen double? 19. (Pg. 172) Why is not the image of an object inverted in the common mirror? 20. (Pg. 172) Your whole figure may be seen in a looking-glass, which is not more than half your height; how is this shown in fig. 3. plate 17? 21. (Pg. 173) Why is the image invisible to the person, when not standing directly before the glass? 22. (Pg. 173) In what situation may a second person see the image reflected? 23. (Pg. 173) In what direction will an object always appear to the eye? 24. (Pg. 173) How is this explained by fig. 4, plate 17? 25. (Pg. 173) What is it that reflects the rays in a looking-glass? 26. (Pg. 174) All opaque bodies reflect some light, why do they not all act as mirrors? 27. (Pg. 174) What substances form the most perfect mirrors, and for what reason? 28. (Pg. 174) What are the three kinds of mirrors usually employed for optical purposes? 29. (Pg. 174) How are the rays of light affected by them? 30. (Pg. 175) What is the form of a convex mirror, and how do parallel rays fall upon it, as represented in fig. 1, plate 18? 31. (Pg. 175) What is represented by the dotted line in the same figure? 32. (Pg. 175) Explain by the figure, how the parallel rays will be reflected. 33. (Pg. 175) At what distance behind such a mirror, would an image, produced by parallel rays, be formed?