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‘Douglas’ Combined Protractor and Parallel Rule


These are two almost identical artifacts. Each consists of a square-shaped cardboard envelope with a cotton string looped around a circular attachment as a closure. On the front of the envelope there is a paper sticker covered in writing about the object.

Inside the envelope there is a flat, square piece of translucent plastic marked with a square grid with the centre lines cross-hatched, and diagonal hatchmarks around each of the four edges. These are numbered in tens in two different scales. The edges of the plastic are slightly beveled. In the centre of the grid there is a small round hole through the plastic.

Accession Number: 2018.ast.49.1-2 (DAA-0058)

Alternative Name:

Primary Materials: Cardboard, Plastic, Cotton String.


On the envelope:
Designed by Commander H.P. DOUGLAS, R.N., Superintendent of Charts, Hydrographic Department, Admiralty, London
(An accuracy greater than half a degree should not be relied upon this instrument).”

Beneath this, there is text that describes the advantages of the instrument and instructions for different types of use.

On the protractor:


Dimensions (cm): Height = 14, Width = 0.3, Length = 14.


This is a marine navigational instrument used to calculate a course or bearing on a chart.


49.1 Fair. The cardboard envelope of the instrument is intact but worn and dirty in places. The string is fraying and particularly dirty. Along its base and at the bottom-right corner, the paper label is damaged and peeling away from the cardboard. On the reverse of the envelope there are a few small black inky marks.

The protractor is in very good condition. There is a small blue mark on the upper side of the plastic and a few small scratches.

49.2 Good. The cardboard envelope is intact. It is slightly scuffed around the edges and dirty across the surfaces, particularly in the bottom right hand corner of the front side, but otherwise in good condition. The cotton string is fraying and unravelling at the ends, and has been broken so it no longer is able to close the envelope.

The protractor is in very good condition. There is a small blue mark on the underside of the plastic, and a few small scratches.

Associated Instruments:

Manufacturer: Unknown

Date of Manufacture: c. 1910-1914


This object was likely moved from the David Dunlap Observatory in Richmond Hill in 2008, upon the sale of the observatory. It was stored at the Department of Astronomy and Astrophysics until 2017, when it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

These instruments were dated by the stated position of the designer H.P. Douglas held the position of Superintendent of Charts from 1910-1914.

Historical Notes: