CHAPTER IV.

38. What is said of the nature of attraction? What was Newton's idea of it?

39. What is said of attraction in solids? What of its different modes of action? What is the difference in attraction in the case of steel and of water? What is said of the freeness with which particles of a fluid move among each other?

40. Explain Fig. 9. Explain Fig. 10.

41. Give the difference between mercury and water in regard to the globular form. What if said of drops of water on leaves?

42. What is said of oil in reference to attraction? Describe and explain the manufacture of shot. What is said of the globular form of the earth and the heavenly bodies?

43. What is said of crystallization? State the examples cited. What is said of the crystallization of water? Give and explain the example of sudden crystallization.

44. What is said of frost-work? What of snow?

45. What is stated in regard to the snow-crystals of the arctic regions? What is said of order in nature? Why can you not make the surfaces of broken glass adhere?

46. Explain the cementing of glass. What is said of the adhesion of pieces of India-rubber? Describe and explain the experiment with bullets and with balls of lead. How may silver and gold be made to adhere to iron? What is said of the adhesion of tin and lead? What of the adhesion of panes of glass?

47. Upon what does the strength of adhesion depend? Illustrate the agency of heat in promoting adhesion. Give familiar examples of attraction between solids and liquids. Explain the experiment represented in Fig. 15.

48. What is said of stems in stagnant water? Explain Figs. 16, 17, and 18.

49. Explain Fig. 19. Explain the rise of fluids in tubes by Fig. 20.

50. What is meant by _capillary_ attraction? Give familiar examples of the rising of liquids in interstices.

51. Describe and explain the process of getting out millstones. How does a blotter differ from writing-paper?