Ship of the line

A Ship of the line was a kind of warship. Most ships of the line were built between the 17th and 19th century. At that time, battles were fought by many such ships, which sailed in a line. At first, such ships were sailing boats, but from about the 1840s, steam-driven ships of the line were built. The steam-powered ships of the line were still made of wood. From about 1859, the Ironclad warship replaced them. 
At that time, ships had cannons. Larger ships had room for more cannons, and were therefore more likely to hit the enemy. Today, ship designs are noticeably different, as cannons are no longer used.