Seafaring men need to know about the tides when they enter or leave harbors. Tides are very different at different places along our enormous coastline, and they change from one day to another. The Coast and Geodetic Survey has worked out a wonderful way of telling ships about tides in advance. Every day, records pour into Washington from all along the seacoast. The figures they give are put into a fantastic “thinking machine,” together with other figures about the sun and moon which cause the tides. Electricity is turned on, and in no time the machine tells what tides will be like with ordinary weather tomorrow or even next month. Men have come a long way since they first learned to float on a blown-up animal skin or a bundle of reeds. For thousands of years, they have been inventing new and better ways to travel across water. But the oceans have an enormous power and force. Science and seamen still have much to learn about the power which they must fight and make work for them--and which will always be exciting. [Illustration] WHAT SEAMEN SAY Here are some words that you haven’t met in the rest of the book. They are all part of seagoing language. [Illustration] [Illustration] [Illustration] AHOY--a call given by men on one ship to greet men on another. AVAST--an officer shouts “avast” if he wants a seaman to stop hauling on a line. BELAY--to tie or make fast. A belaying pin is a short rod which can be stuck into a holder so that a line can be twisted around it. There were many belaying pins on old sailing vessels, and they made handy weapons at times. DEEP SIX--when a sailor throws something overboard, he “gives it the deep six.” The expression comes from the days when sailors measured the depth of water with a leadline. The “deep six” was a place on the line which showed the water was six fathoms (36 feet) deep. [Illustration] [Illustration] [Illustration] [Illustration] FOUL--Seamen use this word to describe anything that has gone wrong or got mixed up. A snarled line is foul. A ship’s hull covered with barnacles is foul. Bad weather is foul. NORWEGIAN STEAM--seamen say they use “Norwegian steam” when they do heavy work without the help of machinery. SCUTTLE BUTT--the drinking fountain on a ship. Because seamen often gather there to talk, the rumors and gossip that they pass on are also called “scuttle butt.” SEA LAWYER--a seaman who likes to argue about rules and regulations. SLOP CHEST--a room where seamen can buy clothes. Every ship is required to have one. SLUMGULLION--a seaman’s word for stew that he doesn’t like. TRAMP--a freighter that ties up anywhere and has no regular schedule. WINDJAMMER--a sailing vessel. [Illustration]