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?
CHAPTER VI.
67. Show what we mean by the centre of gravity by Figs. 30, 31, and 32.
68. Give the definition of centre of gravity, and explain it. What is shown by Fig. 33?
69. How can we find the centre of gravity of a body? What is said of scales and steelyards?
70. State what is represented by Fig. 38. Illustrate the fact that the centre of gravity seeks always the lowest point.