Demonstration Slide Rules #10278 and 10279
Kueffel & Esser, New York
By using logarithms, one is enabled to replace tedious multiplication and division processes by simpler addition and subtraction. Raising numbers to powers is reduced to multiplication. A slide rule is a sort of analog computer device that utilizes logarithmic scales to do these calculations as well as trigonometric problems. Slide rules were extensively used by engineers and physicists until the mid 1970s when electronic pocket calculators made them obsolete. To teach students the use of slide rules, these large demonstration models were made to hang on the walls in the front of classrooms for all to see. These two examples are 85" and 95" in length.
Reference: Welch catalogue (1965) p.927.

Volume Standards #10351
E. & T. Fairbanks and Co., St. Johnsbury, VT
Manufacturers of containers with stated volumes needed to have standards for comparison. It is not clear what purpose these well-made brass vessels served in the Department of Physics, however. And curiously, there are no indications of the volumes marked on them but from the measured dimensions the largest vessel is approximately 1/2 bushel and the others smaller by ratios of about 2, 4, and 16.

Goniometer #10053
Unsigned
A goniometer is a general-purpose instrument used to measure rotation angles. Mineralogists use them to measure face angles of crystals. They are also used in physics, especially in optical polarization experiments.
Reference: Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, pp.290-92.

Colladon Apparatus #10474
Max Kohl, Chemnitz
This large metal tube is filled with water and the cork removed from the small hole near the bottom. It demonstrates the parabolic form of jets of water. Light from a lamp placed by the window opposite the jet opening follows the jet to illustrate total internal reflection.
Reference: Max Kohl Catalogue No.100 (c.1927) p.307.

Plateau’s Apparatus #10470
Max Kohl, Chemnitz
This device has a stirrer rotated by a handle to demonstrate the flattening of a sphere of oil rotating in alcohol.
Reference: Max Kohl Catalogue No. 100 (c.1927), p.312-13.

Free-fall Apparatus #10361
Max Kohl, Chemnitz
A steel ball held by an electromagnet is released by opening a switch controlling the current to the magnet. When the ball falls to the bottom it trips another switch. The time of fall could be measured, e.g., by a tuning-fork chronograph. From this and the distance of fall, the acceleration of gravity can be determined.
Reference: Max Kohl Catalogue No. 100 (c.1927) p.260.

Atwood Machine #10394
Unsigned
The direct method of measuring the acceleration of gravity involves dropping an object and measuring the time of fall for a measured distance. However, timing devices to measure the short intervals of time did not become accurate enough until recent times. Galileo effectively "diluted" gravity by using inclined planes but George Atwood (1746-1807) devised another method. He installed a nearly frictionless pulley at the top of a pillar. A string over the pulley had equal masses M on the string on both sides. Then, when it is unbalanced by adding a small mass m to one side, the system accelerates, but slowly enough to easily measure the times of fall. Since the unbalanced force is provided by m but the total mass to be accelerated is 2M + m, the acceleration of gravity is diluted by the ratio of those quantities. Newton’s Second Law of Motion can also be demonstrated. By using disk weights that pass through rings, the masses can be changed during the motion as the disks pick up or drop off additional bar weights.
References: Gerard L’E Turner, Nineteenth-Century Scientific Instruments, Berkeley, 1983, pp.76, 79; David Wheatland, The Apparatus of Science at Harvard, 1765-1800, Cambridge, 1968, pp.96-97; Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, pp.36-39.

Kater’s Pendulum #10070
Max Kohl, Chemnitz
This 1.7 meter long reversible pendulum has two knife-edges exactly 1 meter apart. A sliding weight is carefully adjusted so that the period of the pendulum is the same when swinging from either knife-edge. The period is then exactly the same as that of a simple pendulum with a length of 1 meter. By timing a large number of oscillations, a very accurate value for the acceleration of gravity can be obtained.
Reference: Max Kohl Catalogue No. 100 (c.1927) p.286.

Rotating-ball Apparatus #10686
Unsigned
The large and small balls are connected rigidly together but can slide back and forth as a unit. When rotated, the pair of balls slides to one end or the other of the wire guide unless they are at the proper balance point for which their distances to the axis of rotation are inversely proportional to their masses.

Maxwell’s Top #10563
Unsigned
A needle on the heavy brass base supports the rotating top at its center of gravity. The positions of the balls around the rim can be varied to achieve balance. A small force causing an unbalance leads to precession of the top.
Reference: Sutton, Demonstration Experiments in Physics, New York, 1938, p.82.

Gyroscope #10383
Unsigned
This simple, wooden gyroscope was used to demonstrate rotational phenomena such as precession, conservation of angular momentum and gyroscopic motion.
Reference: Richard M. Sutton, Demonstration Experiments in Physics, New York, 1938, pp.78-87.

Hipp Chronoscope #10092
Max Kohl, Chemnitz
This instrument, designed to measure short intervals of time to an accuracy of 1/1000th of a second, was invented by M. Hipp of Neuchâtel about 1850. A metal reed, vibrating 1000 times a second, controls the weight driven clockwork. With the clock running, the indicating mechanism is operated by a pair of electromagnets.
References: F.A.B. Ward, Time Measurement, Science Museum Publication, London, 1966; Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, p.115-16; Max Kohl Catalogue no. 50 (c.1911) p.248.

Cavendish Apparatus #10176
Max Kohl, Chemnitz
Using an apparatus designed by Rev. John Michell, the English physicist and chemist Henry Cavendish performed an experiment in 1798 that has been called "weighing the Earth." What he measured was the universal gravitational constant now known as G. Armed with that number, the radius of the Earth, and the acceleration of gravity, one can use Newton’s law of gravitation to obtain the mass of the Earth. The apparatus consists of a pair of small silver balls on a short rod hanging from a delicate torsion fiber. A pair of massive lead spheres is positioned to as to attract the small balls and twist the fiber. From the angle of twist, the tiny gravitational attraction between the lead and silver spheres can be measured.
Reference: Kohl catalog #100, p. 289.