Title: Very Cool Antique Steel Plumb-Bob
Shipping: $7.00
Artist: N/A
Period: 19th Century
History: N/A
Origin: N/A
Condition: Excellent
Item Date: 1800 to 1930
Item ID: 2218
This extremely simple and sensitive old tool is to make and find a vertical line. It can be carried in a small tool box for easy use in the field. This has been precision machined by hand. Plumb bob or plumb line employs the laws of gravity to establish what is "plumb" (exactly vertical) - you don't need a graduate degree in physics to understand that a string suspended with a weight at the bottom will be both precisely vertical AND perpendicular to any level plane through which it passes. The plumb bob, obviously, is the companion tool to the level. A homemade plumb can consist of most any bit of string with a weight tied its end (a couple of washers, say, or a lead sinker from a fishing line. But the factory-made plumb bob has a specially designed weight. Well machined and balanced bobs have pointed tips, that makes them more precise to use.
Link: http://en.wikipedia.org/wiki/Plumb-bob
A plumb-bob or a plummet is a weight, usually with a pointed tip on the bottom, that is suspended from a string and used as a vertical reference line, or plumb-line. The instrument has been used since the time of the ancient Egyptians by bricklayers, masons, and carpenters to ensure that their constructions are "plumb", or perfectly upright. It may also be used in surveying to sight a point on the ground that is not readily visible. Small plumb bobs are included in the kits of various instruments such as levels and theodolites. They are used to set the instrument exactly over a fixed datum marker, prior to taking fresh readings.
