There are several kinds. A suction dredge lowers a great pipe into the harbour mud and pumps great quantities of mud-charged water to the surface. This is run into tanks where most of the mud settles while the water runs over the top. In some cases it is possible for the pipe carrying this mud and water to be led ashore where a low spot is to be filled or where the mud is needed for some other reason. Here the water trickles gradually away, and the troublesome mud that had been silting up a channel is converted, perhaps, into valuable city property. Another type of dredge carries an endless belt on which are great ladle-shaped containers, called “buckets.” One end of this belt is lowered to the bottom. The belt is set in motion, and each gigantic “bucket” dumps the mud of the harbour bottom into a great “well” built into the ship which is capable of carrying a startling quantity. There are other types of less importance than these, but already this chapter has grown beyond the length assigned to it and I must bring it to a close. To pretend for a moment that I have amply described the ships I have mentioned would be, of course, ridiculous. I have done hardly more than mention the more important and more picturesque types of steamships that exist in the world to-day. A book could be written on any one of them, and my greatest hope is that I may interest a few readers who will go to other volumes more complete than mine, in order to learn more of some phase or another of this fascinating subject. Should I be so fortunate I shall be content, for one volume cannot do more than outline what can be found in countless others that have specialized on a thousand phases of the subject I am attempting to discuss. CHAPTER VII SHIPS OF WAR Much of the story of ships is contained in the story of ships of war, which, from time immemorial, have been vital factors in the lives of nations. The Egyptians fought battles on the sea. The Greeks saved their civilization from the armies of Xerxes by defeating the ships of the Persians at Salamis. Rome defeated Carthage because Rome secured the upper hand on the sea. It is true that much of the story of the Punic Wars is the story of Hannibal and Hamilcar, but while Hannibal marched his army from Spain across the Pyrenees, across France, across the Alps, and finally into Italy, where he spent years harrying the land, Carthage owed her downfall to the ships of Rome, as Hannibal owed his final defeat by Scipio Africanus to those ships. Similarly Napoleon, two thousand years later, owed the collapse of his plans not so much to the defeats he suffered on land as the defeats he suffered on the sea at the hands of Nelson and the British Navy.