_Mrs. B._ It certainly is so; though I scarcely dare venture to advance such an opinion, whilst Caroline is contemplating her beautiful rose.

_Caroline._ My poor rose! you are not satisfied with depriving it of colour, but even make it have an aversion to it; and I am unable to contradict you.

_Emily._ Since dark bodies, absorb more solar rays than light ones, the former should sooner be heated if exposed to the sun?

_Mrs. B._ And they are found, by experience, to be so. Have you never observed a black dress, to be warmer than a white one?

_Emily._ Yes, and a white one more dazzling: the black is heated by absorbing the rays, the white is dazzling, by reflecting them.

_Caroline._ And this was the reason that the brown paper was burnt in the focus of the lens, whilst the white paper exhibited the most luminous spot, but did not take fire.

_Mrs. B._ It was so. It is now full time to conclude our lesson. At our next meeting, I shall give you a description of the eye.

Questions

1. (Pg. 179) What is meant by the refraction of light?

2. (Pg. 179) What is believed to be the cause of refraction?

3. (Pg. 180) How is a ray refracted in pa.s.sing obliquely from air into water?

4. (Pg. 180) How is this refraction explained in fig. 1, plate 19?

5. (Pg. 180) What is fig. 2 intended to explain?

6. (Pg. 180) What is the rule respecting refraction, by different mediums?

7. (Pg. 181) What is meant by the perpendicular?

8. (Pg. 181) How does fig. 3, plate 19, elucidate the law of refraction?

9. (Pg. 181) What will be the effect on the apparent situation of the flower?

10. (Pg. 181) What effect has refraction upon the apparent depth of a stream of water?

11. (Pg. 182) How does the atmosphere refract the rays of the sun, as represented, fig. 4?

12. (Pg. 182) Why have we the rays of the sun always refracted?

13. (Pg. 182) What length of time is required for light to travel from the sun, to the earth?

14. (Pg. 182) What effect has this upon his apparent place?

15. (Pg. 182) How is the length of the day affected by refraction?

16. (Pg. 183) How are rays refracted, which fall obliquely upon a flat pane of gla.s.s, (fig. 5, plate 19?)

17. (Pg. 183) What is the reason that objects are distorted, when seen through common window gla.s.s?

18. (Pg. 184) What is meant by a lens?

19. (Pg. 184) What are the five kinds called, represented at fig. 1, plate 20?

20. (Pg. 184) What is meant by the axis of a lens?

21. (Pg. 184) How are parallel rays, refracted by the double convex lens, fig. 6, plate 19?

22. (Pg. 184) What is meant by the focus of a lens?

23. (Pg. 184) What is the focal distance of parallel rays, from a double convex lens?

24. (Pg. 184) How are the rays refracted by a concave lens, fig. 7, plate 19?

25. (Pg. 185) What is the effect of one plane side in a lens?

26. (Pg. 185) How is the focus of the plano-convex lens situated, fig.

2, plate 20?

27. (Pg. 185) How does a convex lens magnify objects, fig. 6, plate 19?

28. (Pg. 185) What is the article denominated which is represented at fig. 3, plate 20?

29. (Pg. 185) How will a ray be refracted, which enters on one side of the prism, in the direction A B?

30. (Pg. 185) What effect is produced by this refraction, as represented in fig. 4, plate 20?

31. (Pg. 186) Of what are the rays of white light said to be composed?

32. (Pg. 186) What colours are produced?

33. (Pg. 186) By what property, in light, does refraction enable us to separate these different rays?

34. (Pg. 187) What experiment may be performed with a piece of card, so as to exemplify the compound nature of light?

35. (Pg. 187) How can the same be shown by a lens, fig. 5. plate 20?

36. (Pg. 187) Is it certain that there are seven primitive colours in the spectrum?

37. (Pg. 188) How is the rainbow produced, and what is necessary to its production?

38. (Pg. 188) How are the solar rays affected by a convex lens?

39. (Pg. 188) Why is such a lens, called a burning gla.s.s?

40. (Pg. 188) Why are bodies of a dark colour, more readily inflamed, than those which are white?

41. (Pg. 189) What is believed to be the reason, why some bodies absorb more rays than others?