Vocabulary Builder #2: B is for Ballast

Ballast are the disposable weights carried by surface ships to keep them on an even keel, and by submersibles, to help them descend and ascend.

In the case of ships, ballast are usually stones. For submersibles - in particular bathyscaphes - it can be gasoline. For submarines, outside water or pressurized air. To blow ballast tanks, the water or air is expelled, causing the submersible to rise. [Typically, a submarine is a submersible in service to the military branch of a country, a submersible is a research vessel.]

Word Origin and History: (link to online dictionary]
1520–30; < MLG, perh. ult. < Scand; cf. ODan, OSw barlast, equiv. to bar bare1 + last load; see last4




Discharge of ballast water (used to keep the ship on an even keel) from a container ship. Foreign ships in their home waters take on this ballast - complete with destructive marine organisms, sail around the world to another port, where they discharge the ballast water, and the marine organisms, into once pristine water.