A remarkable feat of engineering, the Panama Canal covers a distance of fifty-one miles and lifts a ship as high as a nine-story building in order to overcome the high terrain of the Isthmus of Panama.
The canal was built to provide a shortcut for ships traveling from the Atlantic Ocean to the Pacific or vice versa. No longer would they have to make the arduous 7,500-mile voyage around Cape Horn, the southernmost tip of South America.
The original plan for the canal called for cutting through the isthmus with a sea-level channel, and the huge undertaking began that way in the late 1800s. But the rocky continental divide that cuts through Panama turned out to be a formidable barrier, and the cost of cutting down through it was too high.
So three sets of locks were built instead, one near the Atlantic Ocean and two near the Pacific, to lift and lower the ships. The locks are massive chambers, into and out of which water flows. They are built of concrete, and are large enough, at 1,000 feet long, 110 feet wide and 70 feet deep, to accommodate all but the world’s largest military ships and supertankers. The locks are paired so that ships can pass in both directions.
Three man-made lakes, particularly the huge, dam-held Gatun Lake, were built to supply the locks and the channels with water. The immense project was completed in the summer of 1914.
A ship that begins at the Caribbean, or Atlantic, end of the canal enters the Gatun Locks at sea level, guided by tugboats and electric towing locomotives called “mules” on the chamber walls. Steel gates close behind the boat, lake water flows in through valves in the bottom of the chamber, and the ship rises. About ten minutes later the water has risen to the level of the water in the second chamber, and the gates in front of the boat swing out.
The steel doors are nearly silent as they move, says David McCullough, who wrote The Path Between the Seas: The Creation of the Panama Canal, 1870-1914. And, he says, you feel you are riding a slow elevator, except that the elevator is your whole ship.
In the second chamber the water rises again, delivering the ship into a third chamber, where the process is repeated a final time. Ultimately, the boat rises in three steps to a height of eighty-seven feet above sea level.
After passing through the Gatun Locks, the ship travels across Gatun Lake and the isthmus until it nears the end of the canal and the Pedro Miguel Lock. Here, and in the next set of locks called Miraflores, the boat is lowered back to sea level as water pours out of the locks. The ship then takes up its voyage on the Pacific side of Central America, in the Gulf of Panama.
There is often a backlog of ships waiting to move through the Panama Canal, but once en route, ships only need about eight hours to make the passage from ocean to ocean.