27. (Pg. 161) What enables us to see a ray of light in its passage, through a darkened room? 28. (Pg. 162) By what reasoning would you prove that an object, such, for example, as a house, is seen by reflected light? 29. (Pg. 162) Why may one side of such object appear more bright than another side? 30. (Pg. 162) How is the fact exemplified by the sun, or moon, shining upon water? 31. (Pg. 162) Why is this best evinced by moonlight? 32. (Pg. 163) By what light do we see the moon, and why is it comparatively feeble? 33. (Pg. 163) What circumstance, renders objects seen by moonlight, still less vivid? 34. (Pg. 164) What is meant by the pupil of the eye? 35. (Pg. 164) What by the retina? 36. (Pg. 164) How do the rays of light operate on the eye in producing vision? 37. (Pg. 164) How may this be exemplified, in a darkened room? 38. (Pg. 164) What is meant by a _camera obscura_? 39. (Pg. 164) How is it explained in plate 16? 40. (Pg. 165) Why are the objects inverted and reversed? 41. (Pg. 165) What analogy is there between the camera obscura, and the eye? 42. (Pg. 165) Is it the object, or its picture on the retina, which presents to the mind an idea of the object seen? 43. (Pg. 166) By what organs is sensation produced, and how must these organs be affected? 44. (Pg. 166) How will the idea of contact, apply to objects not touching the eye? 45. (Pg. 167) Why do not objects appear reversed to the eye, as in the camera obscura? CONVERSATION XV. OPTICS--_continued_. ON THE ANGLE OF VISION, AND THE REFLECTION OF MIRRORS. ANGLE OF VISION. REFLECTION OF PLAIN MIRRORS. REFLECTION OF CONVEX MIRRORS. REFLECTION OF CONCAVE MIRRORS. CAROLINE. Well, Mrs. B., I am very impatient to hear what further proofs you have to offer, in support of your theory. You must allow, that it was rather provoking to dismiss us as you did at our last meeting. _Mrs. B._ You press so hard upon me with your objections, that you must give me time to recruit my forces. Can you tell me, Caroline, why objects at a distance, appear smaller than they really are? _Caroline._ I know no other reason than their distance.