Sailing employs the wind—acting on sails, wingsails or kites—to propel a
craft on the surface of the water (sailing ship, sailboat, windsurfer,
or kitesurfer), on ice (iceboat) or on land (land yacht) over a chosen
course, which is often part of a larger plan of navigation. From
prehistory until the second half of the 19th century, sailing ships were
the primary means of maritime trade and transportation; exploration
across the seas and oceans was reliant on sail for anything other than
the shortest distances. Naval power in this period used sail to varying
degrees depending on the current technology, culminating in the
gun-armed sailing warships of the Age of Sail. Sail was slowly replaced
by steam as the method of propulsion for ships over the latter part of
the 19th century – seeing a gradual improvement in the technology of
steam through a number of stepwise developments. Steam allowed scheduled
services that ran at higher average speeds than sailing vessels. Large
improvements in fuel economy allowed steam to progressively outcompete
sail in, ultimately, all commercial situations, giving ship-owning
investors a better return on capital.