6CHAPTER XI. THE SMOKE WHICH FALLS.
18CHAPTER XXIII. A PROOF?
7CHAPTER XII. AT THE CENTRE OF THE EARTH.
19CHAPTER XXIV. THE AIR AND THE LUNGS.
8CHAPTER XIII. WHY LEAD IS HEAVIER THAN CORK.
20CHAPTER XXV. OXYGEN.
9CHAPTER XIV. THE AIR-PUMP.
21CHAPTER XXVI. WHY WATER PUTS OUT FIRE.
10CHAPTER XV. DROPS OF RAIN AND HAMMER OF WATER.
22CHAPTER XXVII. PAUL OR GEORGE?
11CHAPTER XVI. AMUSING PHYSICS.
23CHAPTER XXVIII. MY FATHER.
12CHAPTER XVII. WHY THE MOON DOES NOT FALL.
