Menu Close

Plate Measuring Machine


This object looks like a large brass microscope. It consists of a heavy black base with two feet. Rising from this there is a support cylindrical tube with several sections supporting two assemblies of instruments. This tube is hinged just below the stage; it can be tilted so the stage and lens tilts towards the viewer.

The stage of the microscope, mounted about a third of the way up the tube, consists of several layers: at the base, a flat metal support with an adjustable mirror attachment below it. Mounted directly on this, a rectangular box-type structure with a round hole cut in the base. This contains a smaller box which contains a screw which turned by a set of gears and graduated knobs. At the other end, the smaller box is attached to a string which emerges from a small hole in the end of this box. This large and smaller box arrangement serves as the ‘rail’ and ‘carriage’ which permits the assembly on top be moved left and right in very fine increments using the knobs. This top section includes the glass stage; here, two rotating flaps can be moved to hold a sample or slide; the glass in place can be slid out to permit another piece, such as a slide, to be slid in.

Mounted at the top of the support tube of the microscope directly over the stage there is a second cylindrical piece containing the lenses. This can be adjusted via a pair of large knobs on either side of the tube.

Accession Number: 2019.ast.134 (DAA-0050)

Alternative Name: Measuring Engine, Measuring Microscope

Primary Materials:

Metal: Copper Alloy, Metal: Iron Alloy, Glass


Engraved on the lens assembly of the instrument: “Otto Toepfer & Sohn

Engraved on the lens at the base of the lens assembly: “48mm Bausch & Lomb Optical Co.”

Dimensions (cm): Length = 26, Width = 31, Height = 48.5


This artifact, essentially a specialised microscope, is designed to permit the precise measurement of samples or slides. It is very likely that it was used for the analysis of spectroscopic images.

From the Department of Astronomy & Astrophysics catalogue:
“A chief use of this device was to measure the position (and width) of the lines in stellar spectra, for purposes of radial velocity work. Radial velocity is the movement of a celestial objects along the observer’s line of sight, either approaching or receding from the observer. If a star is approaching, the Doppler Effect causes the wavelengths of elemental lines to shift quantifiably towards the blue end of the electromagnetic spectrum, and if a star is receding the lines appear to shift towards the red end of the spectrum. This allows the velocity of a star to be determined relative to the observer or another frame of reference. Programs amassing stellar radial velocities were important for statistically exploring galactic dynamics, morphology, stellar pulsation and atmospheres, and the orbits of spectroscopic binary stars (technical innovations over the last thirty years have rendered radial-velocity detection a leading technique for exoplanet discovery). Similar instruments to the Toepfer were used at observatories from ca. 1900-1965, concurrently with the introduction of ever more sophisticated measuring machines.”


Very Good: This instrument is in very good condition. In places, its metallic surfaces are scratched and corroded, but on the whole the metal is on good condition. Exceptions include the flaps designed to hold the slide in place, and the arm which permits the tilting of the microscope, which are more badly corroded. The mirror at the base is cracked across one side and somewhat scratched and corroded.

Most of the parts of the instrument are present, including all the lenses. The string emerging from the sliding carriage is not attached to anything.

Associated Instruments:

Manufacturer: Otto Toepfer & Sohn

Date of Manufacture: c. 1905-1915


This instrument was likely acquired for astronomical work at the University of Toronto at the beginning of the 20th century. It may have been used into the 1930s, and may therefore have been used at the David Dunlap Observatory. If so, it was stored there until 2009, when the Observatory was closed, when it would have been moved to the Department of Astronomy & Astrophysics at the U of T St George Campus. It was stored here until 2017, when it was moved to a new storage location in McLennan Physical Laboratories.

Additional Information and References:

Historical Notes: