CHAPTER II.

19. What is said of variety in the properties of matter? What of the divisibility of matter?

20. What is said of gold-leaf, and of the wire of gold-lace? What of the soap-bubble? What of the thread of the silk-worm, and of the web of the spider? What of solution of blue vitriol? What of odors?

21. What is said of the dust of the puff-ball? What of pollen? What of the dust rubbed from a moth's wing? What of guano? What of the glazing of visiting-cards? What of the minuteness of some animals?

22. What is said of the Deity in relation to minute animals? What is said of substances called porous? What of those in which there are no pores apparent? What proof is there that all substances have spaces in them?

23. What is said of the amount of space in gases and vapors? Give the statement in regard to steam. What is said of solutions of solids in fluids? What of evaporation? What of the diffusion of odors in the air?

24. What is the relation of heat to space in matter? Upon what do density and rarity depend? Explain tenacity. What is said of this property in gases and liquids?

25. How is the comparative tenacity of substances ascertained? Give the comparative tenacity of various substances. What animal substances have great tenacity? What is said of the value of tenacious substances?

26. What is said of hardness? What of flexibility and brittleness?

27. Give examples of flexible and brittle steel. Explain the actual difference between them. Explain the tempering of steel.

28. What is said of the annealing of glass? What of Prince Rupert's drops? What metals are the most malleable? What the most ductile?

29. What is said of the ductility of melted glass? What of the change of position of particles in making plates and wires of metals? What of welding? What is said of compressibility? What of the incompressiblity of liquids?

30. What influence has heat on the bulk of liquids? Illustrate by the thermometer. What is said of the compressibility of gases? How does elasticity operate in the case of the India-rubber ball?

31. Give the illustration in regard to jumping. State the experiment with the ivory ball. What is said of the movements of particles on each other in elastic substances? What of the degrees of elasticity in different substances?

32. What is the definition of elasticity? What is said of the usefulness of the variety of properties in matter?