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  Surveying Instrument Collection 





Serial Number



Length 326mm, Height 230mm, Diameter 140mm


Surveyor's compass


Used with a chain when traversing, this instrument provided a relatively quick method of measuring horizontal directions in surveying, but not with the accuracy of a theodolite. There are two main kinds of magnetic compass used in surveying, both of which are included in the collection - the Surveyor's compass and the Prismatic compass. The surveyor's compass is usually the larger and more accurate instrument, and is generally used on a stand or tripod. The prismatic compass is often a small instrument which is held in the hand for observing, and is therefore employed for less accurate work. 

This surveyor's compass consists of a long, thin, pointed needle of magnetized steel with a small conical-shaped bearing of agate material at the centre. The end of this needle which points north, the north end, is differentiated from the other end, the south end, by a small metal pin which passes horizontally through the needle near its north end. The agate bearing works on a pointed pivot of hard steel carried at the centre of the low cylindrical metal box (140mm in diameter). Attached to the opposite ends of this box are two sighting vanes with two slow motion screws and clamps which enable a definite line of sight to be defined or laid out. The instrument can either be screwed on to a tripod or remain hand-held for the purpose of measuring magnetic bearings. The metal box carries inside it, three graduated horizontal circles: top and lower circles 0-360 degrees, third circle in quadrants 0-90 degrees, with the N and S directions identified as zero points and the E and W directions are labelled as 90 degrees each.  The lower horizontal circle can read to 3 minutes directly on the vernier. The azimuths are commonly measured on the top circle clockwise from north through 360 degrees. A disc of glass, fitting on top of the metal case, protects the needle and graduated circles.

In this instrument, the needle remains in a fixed position (the position of the magnetic south to north line), while the two upper graduated circles, together with the line of sight, rotate about the vertical axis.

History & comments

While the term 'circumferentor' was consistently used to refer to a surveying compass, a standard form of instrument was not established until the early eighteenth century. Irish and American makers produced significant numbers of circumferentors in the eighteenth century. The instrument was more popular in America than in Britain, and in fact, an entire family of instruments was to develop from the circumferentor in America in the nineteenth century.

There are some doubts about the identity of the inventor of this instrument but it seems likely to have been Gemma Frisius in the first half of the sixteenth century.


In a case


Good, lid of dial ceased up (as on 20 Oct 2000)


  • Signed by Flavelle Brothers & Co. Sydney
  • Catalogued by T. Ko
  • Updated by F. Pall and J.M. Rüeger


Manufactured between 1856-1869. Catalogued in 1997

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