The tank steamship, for carrying oil in bulk, is an American invention. Ship-builders declared for years that no vessel with a shifting cargo, like oil in bulk, would live through a gale, but an enterprising Yankee demonstrated the fact that petroleum could be pumped from the pipe line directly into the hold of a steamship and transported across the ocean in safety. The cost of barrelling the oil is saved, and there is also considerable economy in loading. [Illustration: Cross-section of a Tank Steamship, showing the Expansion Tank.] The tank steamship can always be distinguished by her odd appearance, the funnel being placed a little forward of the mizzen-mast. She has two decks; the hold is divided into from 7 to 9 compartments or tanks for oil; each tank has a capacity of about 4,000 barrels. An empty space of about two feet, called a safety well, is forward of the boilers and engines, separating them from the cargo hold. This empty space, which has a bulkhead on each side, is sometimes filled with water. The depth of the tanks or hold is about 24 feet. On the top of these tanks are expansion tanks, about 5 feet square, reaching to the upper deck, and provided with hatches. The tanks are filled quite full, but sufficient space is left unfilled in the expansion tanks to allow for the expansion of the oil, which is one per cent. in volume for every 20 degrees Fahrenheit. The tanks are filled by means of a very powerful pump, situated at varying distances, from a few yards to one-eighth of a mile from the ship. The greatest care is taken in loading the vessel. A man with a flag is stationed on the ship’s deck, and another man with a flag is placed at the tank. The signal to start and to stop pumping is passed from one to the other. The largest vessel can be filled in about twelve hours. The balance of space between decks is used for storing coal, the ship’s fuel. When the cargo is discharged in Europe the tanks are filled with water ballast for the return trip. [Illustration: Loading a Tank Steamship with Oil, by Force Pumps.] Some of these steamships have been very lucky in picking up disabled passenger steamships, which, of course, means a substantial salvage. There are now about 70 of these tank steamships in the trade, the majority of which are employed by the Standard Oil Company and their connections, and new ones are being constantly added to meet the increasing trade. They are all under foreign flag—English, German, and Dutch—but the Standard Oil Company owns a large interest in them.