The increase in the size of ships is no new phenomenon. The nineteenth century saw a greater revolution in ship-building than that which we are now witnessing. In construction, wood gave way to iron, and in propulsion steam took the place of wind. These changes were not made without provoking a conservative reaction: when Admiral Courbet, then still a young officer, prophesied the end of sail he became the target of much sarcasm. His opponents could not admit that a free source of motive power could ever be abandoned. Everything that is really important and new begins by being regarded with a mistrust that is eventually swept aside: once the possibility of doing better than before exists in fact, no obstacle can stand in its way.

The sea imposes little restriction on the size of ships. Unlike roads, sea routes are not confined within dimensions which limit the dimensions of the traffic they carry. For ships, restriction comes in at each end of the route, in ports, where the depth of water limits their draught. In consequence, we have seen the size of ships increase, during the last decades, in two specifically characteristic ways.