CHAPTER V.

51. What is the attraction of _cohesion_? Give examples of attraction between masses or portions of matter.

52. Explain the falling of a stone to the ground. Illustrate the fact that attraction is mutual. Give the illustration of the ship and boat in full.

53. Illustrate the proportion between the mutual motions of the attracting bodies. Give the calculation in regard to the motion of the earth in attracting smaller bodies.

54. What is said of the universality of attraction? Explain the tides. What is said of the attraction of the moon for the land? What is the difference between the attraction of cohesion and the attraction of gravitation? Why is the word gravitation thus used? What is terrestrial gravitation?

55. Explain Fig. 22. Explain Fig. 23. What is said of substances suspended in different parts of the earth?

56. Explain Fig. 24. What is said of plumb-lines?

57. What is weight? Give the comparison in regard to muscular force. What is said of scales and weights? What of using springs in weighing?

58. What would be the effect on weight if the density of the earth were increased? In what ways would this be perceived? What is said of the variation of weight with distance?

59. What is said of the difference of weight on mountains and in valleys? What of weight in the moon? What of it in the sun? What is said of the different modes of attraction?

60. Show why attraction of cohesion _seems_ to be different from gravitation. Show now that it is really not different. What is said of the experiment with the two bullets mentioned in § 66? What of the adhesion of liquids to solid substances?

61. What is said of the various results of attraction? Explain fully why you can pour water from a pitcher easier than from a tumbler.

62. Explain the operation of the quick movement by which you prevent water from running down the side of a tumbler in pouring it out. What is said of dropping from a vial? How is the size of drops limited? What is said of the movements of drops on window panes?

63. Why are the drops of different liquids different in size? Give the illustration about chalk. Give that about dust. Explain Figs. 27 and 28.

64. Explain Fig. 29. What is said of the difference in size between water and land animals?

65. Give the illustration in regard to trees. Give that in regard to mountains. What is said of the mountains of the moon? What of those of Jupiter? Give the illustrations in § 93 of transgression of the principles which have been elucidated.

66. What is the difference between the attraction treated of in natural philosophy and chemical attraction?