REFLECTIONS ON A 1950 CENCO CATALOGUE
Thomas B. Greenslade, Jr.
Kenyon College, Gambier, Ohio 43022
In my collection I have two sets of images which serve as benchmarks for the classical set of lecture demonstrations that still form much of the basis of today’s physics instruction. One is the set of notes that were published in 1713 to illustrate the lecture series by William Whiston and Francis Hauksbee, and the other is the 1950 catalogue of the Central Scientific Company of Chicago (Cenco). This paper delves into some of the more intersting and significant pieces of apparatus found in these sources.
The Cenco Catalogue
As I write, I can visualize my 1950 Cenco catalogue. It is large, fat and red, a bit like Santa Claus or Father Christmas. When you open it up, you can see that it is a huge collection of wonderful scientific things. It has apparatus which dates back to the middle of the 17th century, and devices that were up-to-date in 1950. Much of the equipment in it we still use in various ways in the student laboratory. It is a convenient summing point for a long period of development in the way in which we illustrate physical phenomena. In this article I will use the apparatus descriptions in the catalogue as a metaphor for some of the 3500 and more pieces of apparatus that I have seen and photographed in museums and back rooms of physics departments in my travels since 1975.
The Hauksbee and Whiston Lectures
My other reference point is the series of lectures by William Whiston (1667-1752) and Francis Hauksbee the Younger (1687-1763) which were given in London in the second decade of the 18th century. These lectures were a commercial venture. The course of twenty six lectures had a subscription fee of two and a half guineas, a rather stiff tuition when translated into modern money. Notes to these lectures, Fig. 1, were published in 1713 in an edition which included engravings of the apparatus, and so we have a very full knowledge of what phenomena were known and how they were demonstrated at the time.
There was a division of labor in the lectures: They were delivered by Whiston, who was Newton’s successor at Cambridge in the chair of mathematics until he was dismissed for heresy, while Hauksbee handled the apparatus.
Hauksbee’s uncle, Francis Hauksbee, the Elder (1660-1713), gave the rationale for the demonstration lectures in the preface to his 1709 book, Physico-Mechanical Experiments:
“The Learned World is now almost generally convinc’d that instead of amusing themselves with Vain Hypotheses, which seem to differ little from Romances, there’s no other way of Improving Natural Philosophy but by Demonstrations and Conclusions founded upon Experiments judiciously and accurately made.”
This Hauksbee was the discoverer of the mercury discharge; when he used the vacuum pump that he developed to evacuate a glass sphere containing a small amount of liquid mercury, he discovered that rubbing the outside of the sphere produced the bluish-white glow that we now identify with discharges in mercury vapor. He was Isaac Newton’s laboratory assistant, who appointed him the experimentalist for the Royal Society in 1703. The twenty six lectures were divided as follows:
I. seven on mechanics,
II. five on optics,
III. three on hydrostatics,
IV. eleven on pneumatics and
V. a fraction of a lecture on “experiments concerning the Electricity of Bodies.”
One reason for the large number of pneumatics demonstrations was that they were new. The vacuum pump had been invented in the middle of the previous century by Otto von Guericke, the Burgomeister of Magdeburg in Germany. At the beginning of the18th century it was still a state-of-the-art scientific instrument, and demonstrations showing its effects were popular. The lectures contain the “Advertisement” below:
“Air Pumps, or Engines for Exhausting the Air from proper Vessels, with all their Appurtenances; whereby the various Properties and Uses of that Fluid in which we Live, are discover’d and demonstrated by undeniable Experiments. Engines for the Compression of the Air: Delightful Fountains, in which the Water, or other Liquour, is made to Ascend by the Force of the Air’s Spring. Syringes and Blow-Pipes, with Valves for Anatomical Injections. Hydrostatical Balances, for determining the Specifick Gravity of Fluids and Solids. The Engine and Glasses for the New Way of Cupping without Fire. Scarificators, which at once make either 10, 13 or 16 incisions.
All of the above-mention’d Instruments, according to their Latest and Best Improvements, are made and Sold by Francis Hauksbee, (the Nephew of the Late Mr.; Hauksbee, deceas’d) in Crane-Court, near Fetter-Lane in Fleetstreet, London.”
The rest of this paper is a comparison of apparatus that appears in Hauksbee and Whiston that was still in use when the 1950 Cenco Catalogue was published. All of these are old friends to the physics demonstrator of the early part of the twenty first century; the phenomena of physics are timeless. My program is to pair pictures of apparatus from 1713 with pictures of apparatus in my own collection or that I have photographed in other collections.
The Cone Rolling Up a Hill
The caption to the device in Fig. 2 says that “This is a Conik Rhombus, or two right cones, with a common Base, rowling (sic) upward to appearance, or from E towards F and G”. The solution to the conundrum is to view the apparatus from the side; the angles of the cones and the tilt of the inclined plane and its spread are adjusted so that the center of mass of the two cones is highest at point E.
The 1950 Cenco catalogue calls this demonstration a “Double Cone and Plane” and lists it at $1.80. However, when I came to Kenyon in 1964 the home built apparatus in Fig. 3 was in the collection as well as a more standard one, and I always used the one that looked like folk art. I suspect that it was made ca. 1925 by Elbe Johnson, a long-time physics faculty member who has earlier appeared in this journal.1
The metal figure of the man wearing a hat rides freely on an axle that connects the two cones. He is counterweighted so that he is always upright. When the system is started at the left-hand side, it moves steadily in what appears to be the uphill direction. In reality, because of the slopes of the two guide rails and the cones, the center of mass of the system is actually getting lower as the system moves.
Force Tables and Resolution of Forces Apparatus
The Force Table in Fig. 4, copied from the Cenco catalogue, has been used since the middle of the 19th century to teach students about the resolution of forces. Despite its strong pedagogical value, this is one of the more boring experiments in the physics curriculum, and I replaced it about thirty years ago with a variant in which the entire laboratory table was used as the force table, with pulleys clamped to the edges. You could always tell when this experiment was being done by the crashes as the weights fell off the mass hangers and hit the floor.
Fig. 5 shows the closest that the Hauksbee demonstrations got to the force table. With the strings applied to the rod at positions A, C and B, and the three arms pivoted so that the forces are applied perpendicular to the rod, the hanging masses are adjusted so that the system is in equilibrium.
The Steelyard is a device long used in trade to weigh objects. It is an unequal arm balance. In the apparatus in Fig. 6 the unknown is hung by one of the two hooks (this gives it a dual range) and the reference mass is moved back and forth along the long arm until the balance is level.
The working principle here is the rotational form of Newton’s first law: For an extended body to be in equilibrium the sum of the clockwise torques must be equal to that of the counterclockwise torques, where torque is defined as the product of the force and the lever arm through which it is exerted. The Romans used this device and, with their skill in engineering, may have invented it. This example is about 50 cm long and is in the Greenslade Collection.
The corresponding apparatus is the Hauksbee and Whiston steelyard in Fig. 7. The accompanying text notes that the several masses are “so adjusted that the Sum of the Motion on one side, made by multiplying each Weight by its Velocity , or Distance from the Center, and so added together, is equal to that on the other side: And so all is still in “Æquilibrio”. This makes perfect sense, except for the seemingly odd usage of the word Velocity. However, at the beginning of the section on Mechanics there is a note that the analysis derives from Galileo’s work on the velocities that result from the applications of forces.
For much of my professional career I have used the slide projector to show audiences and my own students various artifacts that illustrate physical principles. I used Kodak Carousel projectors with their convenient slide trays, but my favorite slide projector is the 500 Watt beast in Fig. 8. This was made in the 1920s by the Victor Animatograph Corporation of Davenport, Iowa, a company otherwise known for making lighting systems for photographers. The lens assembly can be racked out so that an image can be thrown on a far-away screen. Coupled with the very bright light source and its date of production, I think that it was probably used in movie theaters to show still images between silent pictures. I use it to project examples from the set of 550 slides for the teaching of physics that came to me from William Jewell College in Liberty, Missouri.2
These are the standard 3.25 x 4 inch format that was used in the United States.
Hauksbee and Whiston’s “Magic Lantern” in Fig. 9 has all of the parts of the one made two hundred years later, with the main difference being the use of the candle as the light source rather than the 500 Watt projector bulb. The fitting on the left-hand side holds a curved mirror to make fuller use of the candle’s output.
The appearance of the image on a white wall to the right is “to the Surprize of the Spectators.”
In elementary physics we use a series of simple ideas and devices to create more complex ones. One of the most basic ones is the inclined plane in Fig. 10. All makers of physics apparatus sold inclined planes during the first half of the 20th century (and earlier), with a typical cost of $2.00. Some of the planes included protractors attached to the side so that students could easily find the angle of tilt. The example is included because it was made by a relatively little-known company, the Alfred L. Robbins Co., one of many apparatus companies that flourished in Chicago at the start of the 20th century.3
The basic experiment performed with the inclined plane compares the magnitude of the weight of the article being brought up the plane with the hanging weight that supplies the necessary force. Unless you are doing experiments with the coefficient of friction, in which case a flat-bottomed wooden block was used, a cart is used to hold various masses. Figure 11 shows a “Hall Cart”, invented by Edwin Hall (1855-1938). He is known for his doctoral research on the eponymous Hall Effect that today is used for measuring magnetic fields. In 1880 he became a faculty member at Harvard and soon afterward devised the series of experiments that were required for entrance to the institution. This battered cast-iron acceleration cart has seen a lot of use since it was bought ca. 1915 from the L.E. Knott Apparatus Co. of Boston. The device is shown in the laboratory manual published in 1891 by Joseph Bergen and Edwin Hall for the use of high school teachers taking a summer course in experimental physics at Harvard.
The corresponding apparatus from Hauksbee and Whiston is shown in Fig. 12. The accompanying text tells us that this illustration “is an imitation of a Waggon or Coach, …. to be drawn by a Weight on the Scale, either upon an Horizontal, or upon an Inclined Plain, AB, and to go over any obstacle as CB: The Quadrant M, and Bullet N, are to shew the quantity of the Elevation of that Plain, for the Tryal of Experiments relating to all such Sort of Vehicles.”
Wheel and Axle
The text accompanying Fig. 13 notes that “any Weight of Force applied round EF or CD or AB has so much greater power to move the wheel .… about the axis , as the Velocity or Distance from the Geometrical Axis itself is greater.” Translated into modern nomenclature, this says that the larger the diameter of the wheel around which a string or rope is wound, the more effective it is in lifting a weight or producing a force.
The apparatus in Fig. 14 was sold by Max Kohl of Chemnitz, Germany about 1900. It can, of course, be used in the same way as Hauksbee and Whiston suggest. However, it is actually the basis of the differential pulley used today as a lifting device in automotive and machine shops. The two ends of a chain are wound in different directions around the two parts of the axle, and a pulley is suspended from the middle of the chain. A small pull over a large distance on the chain causes the pulley to rise slowly and lift a large weight.
Capillary Rise Demonstrations
The usual Capillary Rise Apparatus consists of a series of fine-bore glass tubes held upright in a water bath. In the demonstration performed by Hauksbee and discussed by Whiston, glass plates (Fig. 15) are brought together at a small angle, and the surface of the water assumes a hyperbolic shape.4
In my teaching days, I did this demonstration with an air wedge formed of two thin glass plates touching on one side and held apart with a spacer on the other side; rubber bands held the wedge together as it was inserted into the pan of water. I always put the demonstration together on the spot, but the example in Fig. 16 at Amherst College in Massachusetts shows a piece of commercial apparatus.
When I got my first pair of glasses about 1946, the optometrist’s office had a series of reproductions of paintings on the history of optics on the office walls. These were commissioned by the optical firm of Bausch and Lomb, and the image that remains firmly in my mind showed Isaac Newton doing his famous experiment of 1666 with a prism. He sits in a darkened room in his home at Woolsthorpe (near Cambridge), with a beam of light coming in through a hole in the shutter. In one hand he holds a prism, and a spectrum of the Sun’s light is displayed on the opposite wall. The word “spectrum” was coined by Newton to aid in discussing the phenomenon.
The experiment can be repeated under controlled conditions using the apparatus in Fig. 17. Here the glass prism has been replaced by a triangular vessel, made with thin glass sides with the vertex pointing down. This is filled with various liquids, and the apparatus is used to measure the index of refraction of the liquids by measuring the angles of incidence and refraction. In modern parlance the apparatus is used to investigate Snell’s Law.
If the apparatus is turned from vertical to horizontal it then takes the form of the spectrometer designed by Robert Bunsen (1811-1899) for spectral analysis.5
The example in Fig. 18 shows a spectrometer in the Greenslade Collection. It was made by the Société Genevoise d’Instruments de Physique in Geneva about 1900. In this form the instrument is used to identify unknown elements in a solid sample. This is vaporized and the light admitted through the slit on the telescope on the right-hand side. Instead of the usual glass prism, a carbon disulphide-filled prism is used to produce the spectrum, which is viewed through the telescope on the left-hand side. The carbon disulphide, a rather smelly liquid, is contained in the closed vessel, and is used because it produces a spectrum that is widely spread out, thus making it easy to locate the spectral lines and with a well known spectrum for comparison. The instrument has a divided circle eleven inches in diameter, which allows angles to be read to the nearest minute.
Air Pumps and Magdeburg Hemispheres
In 1654 Otto von Guericke, the mayor of the German city of Magdeburg, developed a cylinder and piston form of air pump that he used to remove the air from a pair of mating metal hemispheres. Even today this demonstration, on a smaller scale, continues to amaze students. The pump used in their demonstrations by Hauksbee and Whiston is shown in Fig. 19. This is a double-barrel pump in which the two cylinders alternately exhaust air from the glass receiver as the pump handle b-b is moved to the right and then to the left. Deborah Warner of the Smithsonian Institution has used a picture of a similar pump bought by Bowdoin College in the first years of the 19th century in an article on “Air Pumps in American Education”.6
Transylvania was originally chartered in 1780 by the state of Virginia, which assumed that it governed the land to the westward part of the state; this became the state of Kentucky in 1792. The medical department was started in 1799, and the first A.B. degree was granted in 1802. In 1821 Dr. Charles Caldwell of Transylvania made a European trip to buy books and apparatus for the institution, and he bought a number of items from the firm of Pixii in Paris, including this pump.
Fig. 20 Pixii Air Pump at Transylvania University.
This article formed the first part of a talk that I gave at the summer meeting of the American Association of Physics Teachers at San Luis Obispo, California in 1989.
- Thomas. B. Greenslade, Jr., “Elbe Johnson’s Delineascope”, Rittenhouse, 23 (2009), 38-45, and Thomas B. Greenslade, Jr., “Equipping a Physics Laboratory”, Rittenhouse, 18 (2005), 19-30. ↩
- Thomas B. Greenslade, Jr., “John Davis’ Demonstration Slides in Physics”, Rittenhouse, 21 (2007), 25-34. ↩
- Thomas B. Greenslade, Jr., “Apparatus Manufacturers in Chicago, ca. 1900”, Rittenhouse, 13 (1999), 16-19. ↩
- Thomas B. Greenslade, Jr., “Capillary Phenomena”, Phys. Teach., 30 (1992), 300-301. ↩
- Thomas B. Greenslade, Jr., “The Spectrometer”, Phys. Teach., 50 (2012), 152-155. ↩
- D.J. Warner, “Air Pumps in American Education”, Phys. Teach., 25 (1987) 82-85. ↩
- Leland A. Brown, Early Philosophical Apparatus at Transylvania College (Transylvania College Press, Lexington, KY, 1959), pp 5, 7, 85 and 86. ↩
- Thomas B. Greenslade, Jr., “Collection Profile: Visits to Apparatus Collections II – Transylvania University, Rittenhouse, 14 (2000), 107-114. ↩