Ballast

Description

1) A heavy material used to provide weight and/or stability. Ballast is commonly used in hot-air balloons, ships, and submarines. Examples of materials used for ballast include water, sand, and iron.

2) Crushed concrete, slag, or stone used as a foundation for railroad beds.

Authority

• Random House, Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997

• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

• Encyclopedia Britannica, http://www.britannica.com Comment: "Railroad." Encyclopdia Britannica. 3 Sept. 2004 .

• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000