University of Toronto
Scientific Instruments Collection

Tuesday, April 17, 2012

The Transit of Venus

by Paul Greenham

Recent additions to the catalogue include an entire new category: Astronomy. This addition results from joint plans between UTSIC and the Department of Astronomy for a series of events to celebrate the transit of Venus that will take place this year. The transit of Venus is a reliable phenomenon, but it only happens in pairs of years every 120 years or so. This year’s transit, June 5, 2012, will be the last such event until 2117. Moreover, the transit of Venus is highly significant for the UTSIC collection, as the Victoria College telescope, featured on the UTSIC symbol, was the instrument used for one of the main observations of the 1882 transit of Venus in Canada.

The Gregorian reflecting telescope – similar to those used in
the 1761 and 1769 expeditions to view the Transit of Venus.
Thus an exhibit of historical astronomical instruments used at the U of T for the 1882 transit, or related objects (some even dating back to the kinds of instruments used in the 1761 and 1769 transits), seemed inevitable. Although some records of these instruments existed in the previous UTMuSI site, they belonged to the Astronomy Department and we needed to locate them. What ensued was the best kind of collaboration we could hope for with a scientific department.

It should come as no surprise that the Astronomy Department was quite interested in putting on an event for the transit of Venus this year, and very supportive of our interest in cataloguing their old instruments and displaying them. This entailed the now all-to-familiar trip to a cramped room in the basement, where the usual treasure-trove of instruments awaited us. However, as is always the case with UTSIC, admiring shiny brass objects does not translate into neatly categorized, labelled and photographed catalogue entries: some grunt work was required. The vital work of identifying and selecting which instruments would actually go on display was crucially aided by Randall Rosenfeld, the archivist at the Royal Astronomical Society of Canada.

Initially unknown instrument – now identified as a Filar micrometer.
Then, thanks to the templates, instrument handling procedures and cataloguing efforts of a number of the Museum Studies students we have had working for us, we were able to process all the instruments Randall and I had selected. I had direct benefit from these procedures when cataloguing a mystery instrument that seemed designed to screw onto the top of a telescope. After some digging I discovered that this was a filar micrometer, an instrument used to calculate precise distances between distant stellar objects using fine threads moved by micrometers. Those threads, almost invisible at first, turned out to be composed of spider silk! Fortunately for the instrument, I had not in fact brushed away the apparent cobwebs, a caution gained from the handling training our Museum Studies students had imparted.

Astronomical Chronometer – 
used to record precise time
measurements of astronomical 
Close inspection (click on image to enlarge) will reveal spider 
silk threads in the centre that can be moved by micrometers.
Cataloging is not without its frustrations, however, as the precision chronometers were to prove. These chronometers were quite likely the very instruments used to provide the Toronto standard for the 1882 transit. Unfortunately the keys for their casements have somehow been misplaced. At the time of this post various efforts are underway to get into the case, including non-intrusive (non-damaging) lock-picking or procuring skeleton or similar keys from antique clock dealers. If we cannot get into them by the opening of the exhibit (April 28), we may have to display them “as discovered”, a designation that is not without its own historical value.

The exhibit itself will run from April 28 to June 5 (the actual date of the transit). UTSIC and Astronomy are hosting a symposium on April 28 entitled “The Transit of Venus, Past and Present” to highlight the historical and present importance of the transits and also to open the exhibit. This symposium will appeal to those with a serious interest in astronomy and/or the history of science. Speakers include Jay Pasachoff (keynote, Williams College, leading expert on the Sun, planetary transits, and cultural representations of astronomy), James Graham (Director, Dunlap Institute, on the current use of transits in exo-planet research) and Bernard Lightman (York University, on Victorian cultural responses to transits of Venus). The symposium is free, and no registration is required.

For more information and to go to the official website for this event, click here.

Wednesday, February 15, 2012

The Foucault Switch

by Nicolas Sanchez-Guerrero

When researching the history of scientific instruments, scholars hope to complement the physical description of objects with insights on personal, institutional, and experimental histories. These insights result from studying an instrument’s construction and its acquisition, operators, and uses at an institution. Commonly, historical research provides facts and well-founded intuitions, but it also suggests research questions that may remain unanswered. These open questions are gaps in our knowledge about the material culture of an institution, but they can be used to illustrate parts of the process of writing an instrument’s history.

Recently, I started researching an aesthetically interesting and puzzling instrument from the collection of the Department of Physics. Basic notions about the possible workings of this instrument led me to consult online resources for scientific instruments (one of them is the “Physics Museum of Sardinia”) and physics textbooks from the construction period of our instrument. I found that the instrument displayed is a Foucault Switch, a type of automatic circuit interrupter used widely in the late 19th century and invented by the French physicist Jean Bernard Léon Foucault (1819-1868). During that century, scientists and engineers created new uses for electricity and developed increasingly sophisticated circuit elements to control instruments and electric phenomena. Among these elements were different interrupters—basic components that open or close an electric circuit to regulate conduction.

Some devices, such as voltage transformers, require steady sources of non-continuous current. Direct currents supplied to them by voltaic piles or generators must therefore be interrupted periodically. This interruption can be achieved by manually opening and closing a switch, or through an automatic circuit component that successively attracts and releases a pivoting metallic conductor. The Foucault switch is an automatic interrupter in which a balancing rod reacts to an electromagnet, opening and closing the main circuit as it swings like a metronome. Compared to contemporary models, the Foucault switch allowed switching with higher speeds, while permitting the swinging frequency to be regulated.

The UTSIC collection hosts a complete Foucault switch. It is built on a wooden board that holds two cylindrical vessels filled with mercury, an electromagnet made of a pair of coils, and two pairs of terminals to connect a main source and a secondary circuit to feed the electromagnet. Rising vertically, a pivot supports a horizontal conducting balancing rod that reacts to the electromagnet and oscillates, creating contacts through the mercury. A metallic sphere attached at variable height to an extension of the pivot allows changing the oscillation frequency. Copper plates serve as conductors between all circuit elements and an engraved metal plate displays side by side the names of two renowned Paris-based instrument makers of the 19th century—the German-born Heinrich Ruhmkorff (1803-1877) and his French successor Jules Carpentier (1851-1921). This plate suggests that the switch was constructed after 1877, Ruhmkorff’s death year, when Carpentier purchased his workshop.

After defining broadly the instrument’s construction date, the University of Toronto Archives are the natural repository for information about its acquisition and use at the university. The first set of documents that I consulted comes from the “Minutes of the Board of Management”. The succinct records of topics discussed in the board’s meetings show that the board authorized payments for the acquisition of European instruments for the university’s “School of Practical Science”. Particularly suggestive are mentions of purchases, payments, insurance, and utilization of new scientific instruments done by physics professor W. James Loudon (1841-1916) after 1878. This year resonates with the possible construction year of UTSIC’s Foucault switch and with the foundation of the School, which operated from 1878 to 1906. According to the minutes, in 1878 a payment went to the instrument maker Carpentier.

Following this path, two avenues seem fruitful: first, the Archives hold immense voucher books, where researchers can find large amounts of orders and invoices that may shed light on the instrument’s provenance. However, I have not found Carpentier’s invoice. A second possibility lies in investigating Professor Loudon’s personal records for correspondence, notebooks, or orders that could refer to instrument purchases, but the current holdings date back to 1885 and, thus, do not cover the first years of the School. Whether more precise information of UTSIC’s Foucault switch can be found depends on further research, on the invaluable help of the Archives staff, and on a notable degree of fortune around the preservation of archival material and its localization.

Wednesday, January 4, 2012

"Unknown" Instruments

By Erich Weidenhammer
Flagged "unknown" as of January 2012 .

Recently, we added a new search option to the instrument database: a quick list of every instrument that we are currently unable to identify. This simple feature reflects our hope that the catalogue will become a focus for collaboration between those directly involved in the project, the community of scientific researchers at the University of Toronto, and the worldwide community of those interested in scientific instruments.

The entries in the UTSIC database are designed to incorporate new information as it is made available. A minimal entry will provide photographs, dimensions, information on materials, and will list whatever markings are present. Other relevant details, readily available from existing databases, digitized catalogues, and other online sources, will be listed. If the cataloguer is able to identify the instrument on this basis, a name and function will be provided. If not, it will be flagged as “unknown.” We will also endeavour to provide whatever provenance information exists in our records.

The catalogue is able to accommodate a great deal of additional information about provenance, and historical context; however the project does not have the resources to hire dedicated researchers. Detailed contextual information will come from academics who work with the collection for their own purposes. Certainly, the University of Toronto Archives contains a substantial amount of information on various aspects of the collection. Emeritus professors, the traditional guardians of historical apparatus on this campus, are also a wealth of knowledge that we hope to draw on.

Much as we hope that the catalogue will provide a source of interest and historical meaning to the academic community at the U of T, we also hope that it will interest the broader community as well. The precursor to the UTSIC project, the University of Toronto Museum of Scientific Instruments (UTMuSI)—no longer accessible through online search— attracted emails from instrument experts of various stripes from around the world. Its list of “Mystery Instruments” (all now identified) shows the willingness of such people to share their knowledge.

If you have a correction, suggestion, or insight to offer about any object you find in the catalogue, or on the catalogue itself, please share it with us at Like the scientific enterprise that this project seeks to document, we see the cataloguing process as a fundamentally open and collaborative effort.

Tuesday, November 15, 2011

UTSIC Partners with Psychology Department

A Cornell-Coxe Performance Ability Test (1934),
one of many psychological tests belonging to the
University of Toronto Psychology Collection.
by Jennifer Bazar

Over the past year, members of the University of Toronto Scientific Instruments Collection have been working in collaboration with the Department of Psychology at the University of Toronto to establish a partnership. We are pleased to announce that such an agreement has been reached and that we are now working to catalogue a large collection of psychological instruments!

The University of Toronto Department of Psychology holds one of the largest and most extensive collections of psychological instruments and apparatus in North America and is the only collection of its kind in Canada. The items represent the history of the establishment of the first psychological laboratory in the Commonwealth (dating to 1891), the subsequent growth of the University of Toronto’s Psychology Department, and the broader history of experimental psychology. It also contains a large amount of psychological tests dating throughout the twentieth century and demonstration materials from early psychology courses.

The recent work by UTSIC members is not the first time work has been done to catalogue this collection. An e-museum was established several years ago through the work of David Pantalony, University of Toronto alumni and curator at the Canada Science and Technology Museum ( But these initiatives highlight a small handful of the unique and historically-significant instruments and apparatus which form the collection.

The bulk of the collection remains un-catalogued, undocumented, and largely unknown to researchers – but UTSIC and the Department of Psychology are working together to change this. Check back soon for updates on this exciting new project!

Tuesday, September 13, 2011

The Bendix Hygrothermograph: A Mechanical Recorder of Temperature and Humidity

By Erich Weidenhammer

A Bendix Hygrothermograph (Catalogue no. 2011.Bot.2)
Over the spring and summer of 2011, several generous donations have made it possible for us to take the first steps towards museum-quality storage for the UTSIC collection. This post discusses an instrument that came to our attention as we began to think about quantifying the environmental conditions in our storage space.

Temperature and relative humidity (RH) are major considerations for any collection as some materials are particularly susceptible to damage from extremes, or too rapid fluctuations, in either value. The Canadian Conservation Institute (CCI) provides target values for temperature and RH. Established museums, collections and archives, such as the University of Toronto Art Centre, use a variety of HVAC (heating, ventilation, and air conditioning) equipment, as well as sophisticated monitoring instruments, to maintain their collection environments. With the assistance of faculty and students with the Museum Studies program, we will begin to monitor our storage space to determine what needs to be done to maintain a stable environment. 

Measuring values temperature and RH at a given moment isn't difficult. Reasonably accurate and cheap digital instruments are available, for instance, to consumers wishing to monitor a damp basement. Far more useful (and expensive) are instruments that can provide an accurate record of temperature over the cycle of days, nights, and seasons. Reflecting on this problem, we realized that we had instruments that had once been used at U of T laboratories for precisely this purpose. At least one of these, a Bendix Model 594 hygrothermograph appears to be in good condition and is common enough to use (though accompanying documentation suggests that it requires calibration.) Two such instruments were acquired by the Institute for the History and Philosophy of Science and Technology in 2004 from (what was then) the Department of Botany. Unfortunately, our records tell us little about how and where these were operated other than that both are marked “plant pathology”. Surviving documentation suggests that the newer of the two Bendix hygro-thermographs was in use in the early eighties. A second, similar but older, model was last operated in the late sixties as indicated by the chart attached to the recording drum. This second instrument seems to have been last used to only measure temperature.

Two recording drums used with the Bendix 594.
The drum on the left has a one-week temperature
chart clipped to it.
The Bendix 594 with cover open. The shiny bimetallic strip
actuates the top arm marking temperature. Behind it is the
hair bundle that actuates the lower arm, marking RH.
Many will recognize this type of instrument from visits to museums or galleries, where they can be spotted tucked away in corners. Like the Pyro Optical Pyrometer, discussed in a previous post, the Bendix hygrothermograph is still being made, though its maker is now called Belfort Instrument. The heart of the instrument is a mechanical clock housed in a brass cylinder. Instead of turning  hands across a dial, however, this clock turns itself. The cylinder can be set to complete a rotation in either one day or one week—newer instruments use a battery-driven quartz mechanism and will record for 31 days. Old or new, all such instruments incorporate a replaceable chart that is clipped  around the cylinder. A hygro-thermograph chart typically features two scales, one for recording temperature, the other relative humidity.

As the cylinder rotates, each scale is marked by an inked pen. These are actuated by mechanisms that react to atmospheric changes. Temperature is recorded using a still-common method—a bimetallic strip whose deflection changes according to the difference in the thermal expansion of two different metals (usually steel and copper or a copper alloy) that have been joined along their length. 

In 1783, Horace-Bénédict de Saussure introduced his new
method for measuring humidity with a classical
 flourish: a putto playing with another's hair.
The second pen, tracking humidity, is actuated by hair—specifically human hair that has been treated to remove moisture and natural oils. This treated hair will vary in length between 2 and 2.5% across the range of relative humidity. This simple, accurate, and reliable way of recording RH remains relatively unchanged since it was first introduced in the eighteenth century by the Swiss philosopher Horace-Bénédict de Saussure in his Essais sur l’Hygrométry (1783).

While the hygrothermograph is simple and reliable, it shows some of the difficulties embodied in older mechanical approaches to gathering data. Most obviously, it is labour intensive and, no doubt, demands a certain level of skill and experience to use accurately. Modern data loggers (the hygro-thermograph’s digital equivalent) will transfer data directly to a computer. The data from a mechanical hygrothermograph must be read from an inked chart. Charts need to be regularly replaced and the ink refilled. These inked charts accumulate. Using this device on the 24 hour setting would, over time, leave you with a fair amount of cardboard to store. Finally, supplies are not cheap. The slow path of the pens across the chart surface requires special ink and cardboard so that the ink does not dry out or quickly soak into the chart.

Detail of the hair element.
In the end, given issues of calibration and long-term expense, we will likely spring for a digital data logger. It is remarkable, though, that these simple and robust hygrothermographs still have a well-established place in many institutions. They are among the survivors or a generation of instruments that traced data in ink, or smoked paper, against a rotating drum. Many such instruments, from a variety of scientific contexts, will be added to the UTSIC catalogue in the coming months and years.

Saturday, May 14, 2011

Measuring Heat With the Pyro Optical Pyrometer

by Sebastian Assenza

Many extraordinary scientific instruments found their way into the UTSIC collection after being deemed obsolete by one or more of the university’s professors or department administrators. New instruments inevitably supersede older ones which, considering the chronic lack of storage space in modern science departments, are either discarded or donated to museums or private collections. A fascinating exception to this rule is UTSIC’s Pyro Optical Pyrometer, a handheld device used to measure the temperature of an object by comparing reradiated light with a previously calibrated internal lamp.  What makes this particular instrument so special is that similar pyrometers are still being produced and sold by The Pyrometer Instrument Company in New York. A quick comparison reveals that UTSIC’s pyrometer, made in 1940, differs from those sold online today in little but age and experience.

The Pyro Optical Pyrometer is an extremely rugged and easy to use device that serves a number of purposes.  Advertised as an industrial apparatus used to remotely measure the temperature of molten metals or ceramics, the Pyrometer also comes equipped with a sturdy leather case. Along with its light weight, robust construction, and simple operating procedures, the Pyrometer is ideal for work in the field, as well as in the lab or the lecture hall.

Using the Pyrometer is a fairly simple process. The operator stands a safe distance from an extremely hot object (usually about twelve feet) and peers at it through the eyepiece. Inside the Pyrometer is a red lamp that surrounds the user’s view. In order to get a temperature reading, the lamp’s intensity is manipulated, much like the manual focus on a camera, until the colour of the lamp’s light matches that of the desired object. From there, a simple check of the previously calibrated temperature gauge should give you an accurate reading to within 1% of the target’s temperature. The entire process is both simple and reliable.

Our Pyrometer was finally donated to UTSIC in 1996, more than five decades after its manufacture. Despite its age, it remains in surprisingly good condition. The temperature and focus calibrations can still be easily manipulated while looking through the eyepiece and the corresponding gauges can be easily read. Indeed, the only thing preventing the Pyrometer’s use is a missing battery. Such durability and reliability speak to the instrument’s usefulness as a tool for the field, as well as its continued commercial success.

The most striking feature of UTSIC’s particular Pyrometer is the presence of handwritten numbers next to printed degree lines on the temperature gauge. Since the lamp within the pyrometer must be calibrated with a radiating body of a known temperature, the handwritten numbers may be evidence of the actual calibration process undergone by this specific device.  Unique features like this reveal the painstaking efforts that go into creating instruments that must simultaneously be both rugged and precise.

The Pyro Optical Pyrometer is an intriguing example of a multipurpose device that can easily stand up to the rigors of use as both a scientific instrument and a teaching tool.

Wednesday, April 13, 2011

A Professor’s Collection: The L. E. Jones Slide Rules

by Shivangi Trivedi and Erich Weidenhammer

The vast majority of the instruments in the UTSIC collection come from the University of Toronto's science departments. A few instruments, however, have come from private donations to the Institute for the History and Philosophy of Science and Technology.  Among these is a remarkable collection of over 50 slide rules and other mechanical calculating devices donated by the heirs of Professor L. E. Jones (d. June 23rd, 1999). Professor Jones taught applied physics at the University of Toronto from 1936 to 1944 and Mechanical Engineering from 1944 to 1975. A memorial tribute presented to the Council of the Faculty of Applied Science and Engineering on October 7, 1999 paints him as a colourful character—a calligrapher, a poet, a fan of heraldry, and a member of the Monarchist League. In the coming days, all 52 objects of his former collection will be added to the UTSIC catalogue.
Graphical Site Table Slide Rule

Slide rules are remarkable instruments. Before cheap microprocessors made electronic calculators commonly accessible, these simple yet ingenious mathematical tools were used to perform a range of complicated calculations. They were a fixture of mathematical and engineering practice for hundreds of years, from their invention in the 17th century until the mid-1970s and could be found everywhere from grade school classrooms to the Apollo space capsules where they were used as backup calculators. As the collection demonstrates, they varied considerably in complexity, material, propose, and design. Professor Jones’ collection includes not only slide rules, but a variety of other mechanical calculating instruments, from abaci (complete with a detailed instruction book on how to use an abacus) to an arithmometer — a complex wood and brass instrument developed in the 19th century that uses a geared assembly actuated by a crank to add, subtract, multiply and divide.

The UTSICs Tate Arithmometer, an early mechanical computing device.

Although the UTSIC remains focused on instruments used at the University of Toronto, the L. E. Jones Slide Rule collection provides a rare and useful exception. In the spirit of L. E. Jones' eagerness for the material history of engineering computing, the UTSIC will consider further expanding this collection, given the opportunity.