This is a large theodolite inside a wooden box that is painted khaki green. The box is simply made, with a hinged door on one side that can be held shut with two latches. On top of the box there is a metal handle. The box’s corners are reinforced by metal covers. Inside the box, fixed inside the door in a leather pocket with an open bottom, there is a conical plumb bob with a string attached to the top. This is wrapped in brown paper. In another leather pocket on one side of the interior of the box there is a small screwdriver with a wooden handle.
The theodolite stands on a rectangular metal base, supported from a stand in the centre. In one corner of the base, there is a cylindrical piece with a slanted top; inside this, there is a brown circular section. In another corner, there is a wooden cylinder containing three small lightbulbs, two small rods tools stored vertically, and an additional tool that can be accessed by unscrewing the lid of a cylindrical case. The tool is fixed into this lid and has a delicate broad base.
The base of the instrument is circular and made of brass. This supports an adjustable stand with four screw posts supporting the larger circular disk that supports the instruments other components. The disk and components are painted black with a textured surface. The disk base has two roughly triangular supports standing on either side of it, which supports a telescope tube between them on a broad rod, enabling it to be tilted in one dimension. A spoked wheel with a scale around the rim, graduated in degrees, permits the angle of the tilt to be measured. The telescope objective end is covered with a round cover.
At the intersection of the telescope and the support rod, there is a box shape. This connects, through the centre of the spoked wheel to an eyepiece tube with a lens and rubber eyecup at the end. Emerging from the side of this tube there is a second smaller lens. There is a brass knob on the other side of the main tube. A wire runs from the end of the tube around the instrument to a battery case consisting of a pair of vertical cylinders on the other side of the instrument. Beneath the eyepiece tube, there is knob with a central indicator. This has “INCREASE VOLUME” and a directional arrow printed on it.
There are various other knobs, screw and adjustments on the instrument, allowing it to be finely adjusted. In the centre of the disk stand there are a pair of bubble levels set at right angles to one another.
Accession Number: 2017.ast.41
Pibal Theodolite, Broken Transit Theodolite
Metal: Iron Alloy, Metal: Copper Alloy, Wood, Textile (wire insulation)
On a metal label affixed to the disk stand: “SIGNAL CORPS U.S. ARMY
THEODOLITE ML-47-R
SERIAL NO. 154 ORDER NO. 325-NY-41
MADE BY
DAVID WHITE COMPANY
MILWAUKEE WISCONSIN”
In raised lettering on the metal base: “D.W. CO. MILWAUKEE”
Engraved on the brass circle below the adjustable stand: “31/2-8-THDS.”
On a paper label glued to a metal flag affixed to the side of the instrument: “IMPORTANT
TURN OFF SWITCH
TURN RHEOSTAT MAX.
COUNTERCLOCKWISE WHEN FINISHED”
Engraved on the top of the battery case: “USE 2 BATTERIES
BA-30”
Stamped on the base: “S69”
Instrument: Length = 28, Width = 19, Height = 27; Box:
A theodolite is used to measure angles, both horizontal and vertical, in surveying, meteorology, and navigation. The user looks through the device, which is mounted on a tripod, much as one does with a telescope. The purpose of a theodolite is to record accurate angles in order to map precise locations of sites or objects, and create topographical maps.
This model was principally used to ascertain the altitude of weather balloons.
Very Good: The case of the instrument is in a good condition, and intact, although the paint is damaged and nicked across the surface. The paper wrapping around the plumb bob is torn and yellowed; however, the leather pockets inside the care are in excellent condition.
The metal base of the instrument is discoloured and nicked in places, but in good condition. The surfaaces of the instrument are in very good condition. However, in places, the paint surface has chapped off, particularly around the rim of the disk base, and around the circumference of the eyepices tube where it passes through the centre of the spoked wheel. The silver-coloured scale inside the spoked wheel is badly oxidized and blackened.
The lenses and other components appear to be in very good condition. The textile insulation on the visible wires is discoloured where it connects to metal components, but not frayed.
Associated Instruments:
Manufacturer: David White Co., Milwaukee, Wisconsin
Date of Manufacture: 1939-1945
This artifact may have been used for teaching at the Department for the Astronomy & Astrophysics or at the David Dunlap Observatory. If the former, it was probably moved at some point to the Observatory for storage. The sphere was kept at the David Dunlap Observatory until 2009. Upon the sale of the Observatory, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in McLennan Physical Laboratories.
A detailed description of the Pibal Theodolite and its use can be found in the following document:
Interagency Council for Advancing Meteorological Services, FCM-H3-1997 Federal Meteorological Handbook No. 3 – Rawinsonde and Pibal Observations. Washington, DC,
May 1997. (Archived May 30, 2024).
See also:
W.E. Knowles Middleton & Athelstan F. Spilhaus (1954) Meteorological Instruments, rev. 3rd ed. (Toronto – London: University of Toronto Press), pp. 175-189.
Guide to Meteorological Instruments and Methods of Observation, 7th ed. (Geneva: World Meteorological Organization, 2008), 13.2.1.
The early provenance is not know. However, Randall Rosenfeld, Head Archivist at the Royal Astronomical Society of Canada (RASC) offered the following three guesses in an email sent 18 May, 2024.
“a) the instrument seems to have been acquired at a time (ca. 1930s-early 1950s?) when spherical trig., and the simplest type of positional astronomy was still a standard part of the undergrad astronomy curriculum. In performing the observational portion of such assignments any transit or theodolite with decently accurate circles would do. So, by way of example from a very respected contemporary undergrad textbook, see: Henry Norris Russell, Raymond Smith Dugan, & John Quincy Stewart, Astronomy, A Revision Of Young’s Manual Of Astronomy. Vol I: The Solar System (Boston-New York-Chicago-London-Atlanta-Dallas-Columbus-San Francisco: Ginn and Company, 1945), pp. 76, 85-86;
or
b), the generation of astronomers trained at the tail-end of the 19th century, and the first couple of decades of the 20th, would have been very familiar with what Aubin et al. have labelled as “observatory sciences” (The Heavens on Earth: Observatories and Astronomy in Nineteenth-Century Science and Culture, ed. David Aubin, Charlotte Bigg, & H. Otto Sibum [Durham NC-London: Duke University Press, 2010]), which included what is now hived off into surveying and cartography, meteorology, geophysics, etc., meaning it would seem just natural to have some of the apparatus primarily used for meteorology at an astronomical observatory. So an artifactual manifestation of an old habit of thought, if you like; [Likely had its origin in “Humboldtian” science.]
or
c), some scientists just like instrumentation, theirs and that proper to other disciplines(!), so if an instrument is even just barely tangentially connected to their quotidian practice of science, they gladly add it to their physical environment.
None of these explanations need be mutually exclusive.”