CONTEXTS. v 



PAGE 



producing extraordinary effects on epidemic diseases The 

 periodical wind called Harmattan from the interior of Africa. 13. 

 Question discussed as to whether the Earth at any former epoch 

 has been struck by the solid nucleus of a Comet Its consequences. 

 14. Questions discussed as to whether the geographical con- 

 dition of the Earth has ever been disturbed by the near approach 

 of a comet, and whether the Biblical Deluge can have been 

 produced by such a cause. 15. Probability of the terrestrial 

 equilibrium being injuriously deranged by near approach of a 

 Comet reduced to nothing. 16. Opinions of Laplace. 17. 

 Curious phenomena of Biela's comet 81 



COMMON THINGS. WATER, 



1. Water may be solid, liquid, or vapour. 2. Colourless and tasteless. 

 3. Its weight. 4. Expands by heat. 5. Point of greatest 

 density. 6. Freezing-point. 7. Boiling. 8. Evaporation. 9. 

 Heat absorbed in evaporation. 10. Superficial evaporation. 

 11. Saturation of air by vapour. 12. Process of drying. 13. 

 Case of roads and paths. 14. Drying linen. 15. Wind promotes 

 drying. 16. Water never naturally pure. 17. Contains fixed 

 air. 18. And other substances in solution Hard water. 19. 

 Soft water. 20. Mineral springs. 21. Filtration. 22. .Filtering- 

 paper. 23. Artificial filters. 24. Water not absolutely colour- 

 less. 25. How to obtain water absolutely pure. 26. Rain 

 water nearly so. 27. River water Thames water. 28. Water 

 not an element Its composition. 29. Methods of purifying it. 

 30. Distillation of water. 31. Conversion of vapour into 

 water. 32. Weight of vapour. 33. Condensation. 34. Dis- 

 tilling apparatus. 35. Composition and decomposition. 36. 

 Oxygen and hydrogen. 37. Hydrogen. 38. Fitted for balloons. 

 39. Inflammable. 40. Water produced by combining oxygen 

 and hydrogen. 41. Apparatus for this experiment. 42. Com- 

 position of water. 43. Analysis of water. 44. By voltaic 

 current. 45. By other methods. 46. By potassium and sodium. 

 47. By iron 97 



THE POTTEL'S ART. 



CHAP. I. 1. Antiquity and general estimation of the art. 2. Its 

 materials and their treatment. 3. Potter's wheel. 4. Allusions 

 to the art found in ancient writers. 5. Ancient drawings in 

 Theban catacombs. 6. Processes of potters 1900 B.C. 7. Homel- 

 and the potters of Samos. 8. Ancient tombs containing pottery 

 excavated near Naples. 9. Proofs of their antiquity. 10*. 

 Campanian sepulchral chamber with pottery. 11. German 

 sepulchres. 12. Cup of Arcesilaus. 13. Ancient Greek potters. 

 14. Chinese traditions of pottery. 15. Chinese pottery found 

 at Thebes. 16. Porcelain works of King Te Tching. 17. Pro- 

 cesses practised there 113 



