_Mrs. B._ Friction, (as we observed in a former lesson,) may be diminished by polishing, but can never be entirely destroyed; and though fluids, are less susceptible of friction, than solid bodies, they are still affected by it. Another reason why a fountain will not rise so high as its reservoir, is, that as all the water which spouts up, has to descend again, it in doing so, presses, or strikes against the under parts, and forces them sideways, spreading the column into a head, and rendering it both wider, and shorter, than it otherwise would be. At our next meeting, we shall examine the mechanical properties of the air, which being an elastic fluid, differs in many respects, from liquids. Questions 1. (Pg. 129) Why do not the frequent rains, fill the earth with water? 2. (Pg. 129) Why will vapour rise? to what height will it ascend, and what will it form? 3. (Pg. 129) How may drops of rain be formed? 4. (Pg. 130) What becomes of the water after it has fallen to the earth? 5. (Pg. 130) What is the difference between rain water, and that from springs? 6. (Pg. 130) Why is rain more pure than spring water? 7. (Pg. 130) Why is spring water more agreeable to the palate? 8. (Pg. 131) What causes the water to collect and form springs? 9. (Pg. 131) Why cannot water penetrate through clay? 10. (Pg. 131) What is represented by fig. 9, plate 13? 11. (Pg. 132) How can you account for its rising upwards, as represented at C? 12. (Pg. 132) In conveying water by means of pipes, how must the reservoir be situated? 13. (Pg. 132) What is the instrument called, which is represented in plate 14, fig. 1,--and how does it operate? 14. (Pg. 133) Why are wells rarely well supplied with water, in elevated situations? 15. (Pg. 133) When water is found in elevated situations, whence is it supplied? 16. (Pg. 133) Wells and springs, at some periods well supplied, fail at others; how is this accounted for? 17. (Pg. 134) Some springs flow abundantly in dry weather, which occasionally fail in wet weather, how may this be explained? 18. (Pg. 134) What is meant by intermitting springs? 19. (Pg. 134) Whence do rivers, in general, derive their water? 20. (Pg. 134) Why do springs abound more in mountainous, than in level countries? 21. (Pg. 135) How are lakes formed? 22. (Pg. 135) What causes water to rise in fountains, and how is this explained by figure 2, plate 14? 23. (Pg. 135) Why will not the fountain rise to the height of the water in the reservoir? CONVERSATION XII. ON THE MECHANICAL PROPERTIES OF AIR. OF THE SPRING OR ELASTICITY OF THE AIR. OF THE WEIGHT OF THE AIR. EXPERIMENTS WITH THE AIR PUMP. OF THE BAROMETER. MODE OF WEIGHING AIR. SPECIFIC GRAVITY OF AIR. OF PUMPS. DESCRIPTION OF THE SUCKING PUMP. DESCRIPTION OF THE FORCING PUMP. MRS. B. At our last meeting we examined the properties of fluids in general, and more particularly of such as are called non-elastic fluids, or liquids.