Ballast. In order to increase the stability of ships, which have to be dispatched without cargo and to ensure that the propeller will be immersed sufficiently, say about two-thirds of its diameter, a sufficient quantity of ballast will be loaded before sailing. The quantity of ballast depends on the type of vessel, quantity of water which can be taken in the ballast tanks and also the voyage to be made. Seasonal weather conditions which may be expected on the voyage must also be considered.