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A large wooden case contains a disassembled metal instrument and several components. The main components of the metal instrument are either finished in a black crackle paint or, in the case of four steel bars, are polished steel. As listed in the accompanying instructions, these main components are: (See accompanying scanned photo for labelled parts.)

In the top half of the case:
– Item 6 (x2): Steel bars.
– Item 6a (x2): Bar extensions.

In the bottom half of the case:
– Item 2: Left-hand mirror frame with mirror.
– Item 3: Right-hand mirror frame with mirror.
– Item 4: Mirror assembly centerpiece.
– Item 7 (x2): Leg adjustments
– Item 8: Hanging mirror bracket

The artifact includes a number of smaller items:
– 1 key for the lock on the front of the wooden case along with a small, yellowed envelope labelled “Key for Seelyscope #105”
– 1 cardboard-wrapped spare bulb for the Seelyscope. This is labelled as “General Electric 15T7. D. C. // 12257”
– 2x small (4.5 x 4.5cm) mirrors along with a small, yellowed envelope labelled “Seelyscope #105// 2 small fully-silvered mirrors”
– 1 small (4.5 x 4.5cm) partially silvered mirror.
– 1 larger (11 x 11cm) mirror. This is fractured into three pieces and has been repaired with tape.
– 7x small (4.5 x 4.5cm) lenses, each of which has its magnification engraved on its surface. This is accompanied by an envelope labelled “Seelyscope #105 // 7 Lenses for Parallax correction// 1 each 8, 9, 10, 11, 12, 13, 14 inch focal length”.
– 1 small (~1.5 x 1.5 cm) metal clip-like component.

The item also includes the following images and documents:
– 1 photograph of the instrument disassembled in its case
– 1 photograph of the instrument assembled
– 1 set of “Instructions for Assembling & Maintaining the Seelyscope”

Accession Number: 2019.for.16

Alternative Name: Duoscope, Mirror Steroscope

Primary Materials: Steel, Wood, Glass.


Both main mirrors have labels that include the following information:
“Seelyscope No. 105”
“Can Pat. No. 392,431”
“US Pat. No. 2,229,424”

A shipping label on the top surface of the case reads:

Dimensions (cm):

Box: Height = 12, Width = 106, Length = 38.


The seelyscope is a cartographic instrument that superimposes the reflection of a target image into a drawing surface while magnifying that image to the size required for the drawing.

This instrument is essentially a mirror stereoscope in which each eye sees a different image, and the distances between the eye and the image being viewed can be adjusted to control magnification.

Typically, the target image is an aerial photograph that is used to draw a map, or to add detail to an incomplete map.


Very Good: The 11 x 11cm mirror is broken. The black paint has been abraded away in certain locations. The wooden case is worn and nicked.

Associated Instruments:


Spartan Air Services Limited, Ottawa, Ontario.

Date of Manufacture: c. 1940s


This artifact used to create maps from aerial photographs at the University of Toronto Department of Forestry.

It was acquired on July 3rd, 2019 from Tony Ung at the Department of Forestry.

Additional Information and References:

– The digitized files for the Canadian patent 392,431 <a href=”″>are available</a> through the website of the Canadian Intellectual Property Office.

– The Ingenium online instrument catalogue <a href=””>has several examples</a> of this instrument. (Accessed July 5, 2019).

– Robinson, J. M. “<a href=”″>Harold Emery (Si) Seely</a>” <i>The Forestry Chronicle</i> June 1981, 96-98. (Accessed July 5, 2019).

– Seely, H. E. “The Duoscope” <i>Photogrammetric Engineering</i>7, (1941): 18-21.

– Spear, G. A. “The Seelyscope.” <i>Forest Air Survey Leaflet No.4</i>, Forestry Branch, Department of Resources & Development, Ottawa. 1949.

– Spurr, Stephen H. <i>Aerial Photographs in Forestry.</i> New York: The Ronald Press Company, 1948. pp. 112-113.

Historical Notes:

The seelyscope was patented by Harold Emery (Si) Seely of Ottawa, Ontario (b. June 3, 1898) in 1940. When described by Seely in 1941, and in some other literature, the instrument is called a “duoscope”.

It can be compared to a number of similar optical instruments for creating maps from aerial photographs such as the rectoplanigraph, the reflecting projector, the multiscope, etc. This technology is described in contemporary literature on photogrammetry, cartography, forestry, and so on.

Using the seelyscope, each eye viewed a different image and the images were superimposed in the brain. Images were aligned with the aid of reticles in the eyepieces. This process was reportedly difficult to control and could cause severe eyestrain. [Spurr, 113].

The instrument was produced for the Dominion Forestry Service of the Department of Mines and Resources (now Natural Resources Canada), where Seely spent his career. There he developed new methods for applying aerial photography to forestry and cartography. (For details see Robinson 1981.)

The instrument was produced by Spartan Air Services of Ottawa, Ontario, a company engaged in aerial surveying that had been founded by RCAF veterans. Parts of the early versions (perhaps later versions as well) were produced at the machine shop of the Dominion Observatory in Ottawa. [Seely, 21]


  • Donated to UTSIC