Jacob's staff

American  

noun

plural

Jacob's staves

1. Astronomy. cross-staff.

2. Surveying. a pole providing a firm support for a compass or other instrument.

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Jacob's staff British  

noun

1. a medieval instrument for measuring heights and distances

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Etymology

Origin of Jacob's staff

First recorded in 1540–50

Example Sentences

The instrument is mounted on a tripod or Jacob's staff by means of a socket on the underside.

From Project Gutenberg

Just previous, we were given a quick intro/review on how to use a Brunton compass and a Jacob’s staff.

From Scientific American

It is clearly a case of one fraud patronizing another, and when Hudibras sees the astrologer's ludicrous array of tools�a stuffed crocodile, a Jacob's staff�he feels duped, and the two men quarrel.

From Time Magazine Archive

Also, the name of the geometrical cross called Jacob's staff.

From Project Gutenberg

Lying upon the Calendar Stone was what at first I took to be a cross-bow made of gold; but more careful examination convinced me, especially in view of the place where I had found it, that this certainly was an arbalest—called also a Jacob's staff and a cross-staff—such as in no very ancient times, until the invention of the quadrant, was used by Europeans in taking the meridional altitude of the sun and stars.

From Project Gutenberg