Tar

Tar is a naturally occurring black oily substance, which is a byproduct of petroleum. It is very sticky and has a relatively low melting point. In some parts of the world, tar comes to the surface and forms tar pits (eg. the la Brea tar pits[?] in Los Angeles). Before the development of inherently waterproof substitutes, tar was used as a roofant seal for shingles, and also to seal the hulls of ships and boats and to waterproof sails. It is also a vital componant of the first sealed or tarmac roads.

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For the computer term, see also TAR file format