0140
   OPTICAL SQUARE  
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  Surveying Instrument Collection 

Maker

Precision Instruments Co., Sydney

Model

N/A

Serial Number

N/A

Dimensions

Length 35mm, Width 35mm, Height 25mm

Image

Optical Square

Description

This instrument is also referred to as a 'prism square' and it consists of a prism of glass protected by a square metal shield. It is a small pocket instrument, slightly larger than a wrist watch and is typically used for setting out a line at right angles (90) to another. It is considered to be an easier and quicker solution than the use of a theodolite, notably when taking approximate offsets from a chain line.

See also item 0181 in this collection.

History & comments

The optical square uses the 'laws of reflection of light' as it's basic principle. The instrument was invented in 1740 by a London mechanic by the name of Adams (1720-1773).

Conservation

In a case

Condition

Good

Remarks
  • Instrument donated by T. Aspray
  • Catalogued by T. Ko
  • Updated by F. Pall

Dates

Manufactured in 1930 (approx). Catalogued in 1997

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