CHAPTER LVI.--Dredging in modern times--What it has taught us--Deep sea soundings--First attempts--Implements used for it--The chance for inventors--The temperature of the sea--Deep sea temperature--Self-regulating thermometers--Serial temperature soundings--Animal life of the sea--Deep sea dredging--The dredging apparatus of the Porcupine 652 CHAPTER LVII.--The development of ship building--New models for ships--Steam ship navigation--Monitors--Iron-plated frigates--Tin-clads--Rams--Torpedo boats--Their use in the Confederacy--Life Rafts--Yacht building--Ocean yacht race--The cost of a yacht 673 CHAPTER LVIII.--Our knowledge of the earth and sea--How it has increased--The earth the daughter of the ocean--The opinion of science--The mean depth of the ocean--The extent of the ocean--Its volume--Specific gravity of sea-water--Constitution of salt-water--The silver in the sea--The waves of the sea--The currents of the ocean--The tides--The aquarium--The commerce of modern times--The spread of peace 696 LIST OF ILLUSTRATIONS. No. Page 1. Gigantic Cuttle Fish _Frontispiece._ 2. Asiatic Deluge 18 3. Hand of Satan 19 4. Stormy Petrel 30 5. The First Navigator 31 6. Modern Row Boat 33 7. The Deluge and the Ark 35 8. Noctulius Miliaris 45 9. Supposed form of the ship _Argo_ 54 10. The World, according to Homer 61 11. The Earth, according to Anaximander 62 12. The Great Penguin 64 13. Greek Vessel of the 6th Century 65 14. The Ptolemy Philopator 72 15. Common Penguin 74 16. The Sacred Promontory 78 17. Plan of Pythias' Voyage 79 18. Plan of the Voyage of Nearchus 83 19. Supposed form of the ships of Nearchus 91 20. Venetian Galley of the 10th Century 92 21. Wedding the Adriatic 95 22. Danish vessel of the 10th Century 99