Many of the ships run between ports on Lake Huron and Lake Superior. Lake Superior is 22 feet higher than Lake Huron. So ships must use a sort of ladder to get from one to the other through a canal called the Sault Sainte Marie--or Soo for short. Locks in the canal are the ladder-rungs. Suppose a ship is going up. She enters the narrow canal. Ahead are gates. Gates close behind her. She is in a lock. Now the gates in front open and let more water into the lock, lifting the ship higher. She moves forward into another lock and is lifted again in the same way. Sometimes as she goes along, seamen on board toss money to ice cream sellers on shore, and catch the pop-sticks that are thrown back. For eight months each year, the Lake ships keep hurrying back and forth between Detroit, Cleveland, Buffalo, Chicago, Duluth and other port cities. There’s hardly a time when a man can’t see smoke from other vessels on the horizon. Then winter comes, and the Lakes freeze over. Lake sailors tie up their ships and go ashore. Most of them have been on the water day and night through the whole season. Sometimes a ship stays out too late in the year and can’t get to port because ice has locked her in. Then a ship called an ice breaker comes to her rescue. An ice breaker smashes up ice early in the spring, too, so that ships can begin to move. [Illustration] [Illustration: Oil Tanker] [Illustration: Coastal Lumber Carrier] [Illustration: Types of Cargo-Passenger Ships] [Illustration: Banana Ship] [Illustration: Coastal Freighter] [Illustration: Collier] [Illustration: Seatrain] AMERICAN MERCHANT SHIPS Merchant seamen man all the different kinds of cargo ships you see in the pictures on these two pages. Their jobs take great skill and patience and very often courage. It has always been that way with men who follow the sea. Some of the things they do are as old as ships themselves. But many things are different now. On old sailing vessels, the crew had to get their sleep wherever they could find a place to lie down. They might curl up on a coil of rope or on the cargo in the hold. Later, they were given one room, the forecastle, for the whole crew. Everybody was on watch at least twelve hours a day. It is only in the last twenty years that seamen have worked eight regular hours a day. [Illustration: Types of Freighters in Hawaiian Trade] [Illustration: Mariner Class Freighter] [Illustration: Harbor Tug] [Illustration: New Type Freighter] [Illustration: Ocean-Going Tug] [Illustration: Victory Class Freighter] [Illustration: Liberty Ship]