_Mrs. B._ Having explained the mechanical properties of air, I think it is now time to conclude our lesson. When next we meet, I shall give you some account of wind, and of sound, which will terminate our observations on elastic fluids. _Caroline._ And I shall run into the garden, to have the pleasure of pumping, now that I understand the construction of a pump. _Mrs. B._ And, to-morrow, I hope you will be able to tell me, whether it is a forcing, or a common lifting pump. Questions 1. (Pg. 136) Into what two kinds are fluids divided? 2. (Pg. 136) There are different kinds of elastic fluids, in what properties are they alike, and in what do they differ? 3. (Pg. 136) In what particular do elastic, differ from non-elastic, fluids? 4. (Pg. 136) What is meant by the elasticity of air? 5. (Pg. 137) What is said respecting the weight of the atmosphere? 6. (Pg. 137) Why do we not feel the pressure of the air? 7. (Pg. 137) What would be the effect of relieving us from atmospheric pressure? 8. (Pg. 138) How may the weight of the air be shown by the aid of the air pump, and a piece of bladder? 9. (Pg. 138) How is this explained? 10. (Pg. 138) How may its elasticity be exhibited, by an apple, and by a bladder? 11. (Pg. 139) What is the absolute weight of a given column of atmospheric air, and how could its whole pressure upon the earth be ascertained? 12. (Pg. 139) How can the weight of a small bulk of air be found? 13. (Pg. 140) In ascertaining the weight of air, we take account of its temperature--Why? 14. (Pg. 140) How could you ascertain the specific gravity of air, and what would it be? 15. (Pg. 140) What are the essential parts of a barometer, as represented plate 14, fig. 3? 16. (Pg. 141) What sustains the mercury in the tube? 17. (Pg. 141) Of what use are the divisions in the upper part of the instrument? 18. (Pg. 141) To what height will the mercury rise, and what occasions this height to vary? 19. (Pg. 141) When is the mercury highest, in wet, or in dry weather? 20. (Pg. 141) What occasions the sensation of oppression, in damp weather? 21. (Pg. 142) Why will the barometer indicate the height of mountains, or of balloons? 22. (Pg. 142) Is any inconvenience experienced by persons ascending to great heights, and from what cause? 23. (Pg. 142) What occasions the rise and fall of the mercury, in a thermometer? 24. (Pg. 142) To what height will the pressure of the atmosphere raise a column of water? 25. (Pg. 142) What governs the difference between the height of the mercury, and of the water? 26. (Pg. 143) How does the common pump, raise water from a well? 27. (Pg. 143) What is meant by a piston? 28. (Pg. 143) Describe the construction, and use, of a valve. 29. (Pg. 143) What are the parts of the pump, as represented, fig. 4, plate 14.? 30. (Pg. 144) How do these parts act, in raising the water? 31. (Pg. 144) In what does that which is commonly called suction, consist?