Mercury Ripples Dish

Mercury Ripples Dish #10359
Max Kohl, Chemnitz
A heavy iron base has an elliptical dish to hold a pool of mercury. An eye dropper positioned over the focus of the ellipse allows a drop to fall, setting up waves which, after reflection from the sides, converge to the other focus. In earlier times people were not as concerned with the health risks of mercury vapor as we are today.
Reference: Max Kohl Catalog No. 50 (c.1911) p.413.

Acoustic Resonators

Acoustic Resonators #10006
Rudolph Koenig, Paris
The Helmholtz resonators in this set of 14 were used in several ways to analyze the frequencies of sound waves. A tapered tube at the end of each one is to be inserted in the ear. From the sounds of random frequencies entering the tube at the other end the resonator selects and amplifies only the frequency to which it is tuned. Since changing its volume will vary the tuning of a resonator, each one is made with two sections that can be slid apart. A scale on each indicates the frequency. Resonators were also used to determine the intensities of various overtones in musical sounds.
Rudolph Koenig (1832-1901) was the premier acoustical instrument maker in the world in the last half of the 19th century. His instruments were of the highest quality and he personally inspected each one before it went to his customers.
References: Paolo Brenni, Bulletin of the Scientific Instrument Society 44, 13-17 (1995); Thomas Greenslade, The Physics Teacher 30, 518-24 (1992); Gerard Turner, Nineteenth-Century Scientific Instruments, Berkeley, 1983, 143-44; Max Kohl Catalogue No.50 (c.1911) p.450; Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, pp.308-10.

High Frequency Tuning Forks

High Frequency Tuning Forks #10320
Rudolph Koenig, Paris
These tiny precision tuning forks produce sounds at and above the upper range of human hearing. They are individually stamped: UT9 32768, RE9 36864, MI9 40960, and FA9 43690.6. The numbers give the frequencies but they are in units of half vibrations per second, a system used in France in the 19th century, rather than in units of whole vibrations per second or Hertz, the system universally used today. Thus the frequencies range from 16,384 to 21,845.3 Hz. The letters are from the designation of the steps in the musical scale; do, re, me, fa, sol, etc. The symbol "ut" is an earlier version of "do." The subscript 9 is the octave number starting with UT1 which is 64 Hz.
References: Thomas Greenslade, The Physics Teacher 30, 518-24 (1992), Paolo Brenni, Bulletin of the Scientific Instrument Society No. 44, 13-17 (1995).

Tuning Fork Set

Tuning Fork Set #10693, etc.
Rudolph Koenig, Paris
The largest fork in the set is labeled UT2 256 VS. This is equivalent to a frequency of 128 Hertz. The set is incomplete and some of the wooden resonators are replacements.

Galton’s Whistles

Galton’s Whistles #10021, 10022, 10023, 10024
Two by Rudolph Koenig, Paris; one by Central Scientific; one unsigned
Air blown into these whistles, either by a rubber bulb or by lungpower, produces high-pitched sounds near or above the limit of audibility of the human ear. This limit is often taken to be 20,000 Hz, but it is quite variable, depending on the age of the listener and other factors. Dogs and other animals are able to hear sounds of higher frequencies than humans can.
References: Max Kohl Catalogue No.50 (c.1911) p.445; Robert Bud and Deborah Jean Warner, Instruments of Science: An Historical Encyclopedia, New York, 1998, pp.255-56; Central Scientific Catalog F (1923), p.297.

Large Tuning Fork Apparatus

Large Tuning Fork Apparatus #10446, 10447 and 10007
Rudolph Koenig, Paris
Two massive stands have holders for large tuning forks and electromagnetic drivers. The two units are used together to show the combination of simple harmonic motions on a sooted glass plate mounted on one fork. The other fork has a scriber in contact with the plate. Lissajous figures are scratched on the plate if the vibrations are at right angles, and interference effects, such as beats, are shown if the vibrations are parallel.
Reference: Max Kohl Catalogue No.50 (c.1911) p.454-55.

Organ Pipes

Organ Pipes #10010, 10015
James Queen, Philadelphia and Max Kohl, Chemnitz
The longer pipe has three manometric capsules. These capsules have a membrane with the illuminating gas flowing on one side while the other side is open to the inside of the organ pipe. By using a rotating four-sided mirror, one can see images of the flames flicker if there is a varying pressure at that point inside the pipe. At a pressure node there is no variation, while at the antinodes there is. This system also shows the presence of overtones. The shorter pipe is a reed pipe with a rod to adjust the length of the reed.
References: Max Kohl Catalogue No. 100 (c.1927) p.358; James W. Queen & Co. Catalogue of Physical Instruments, 28th edition, Philadelphia, 1888, p.52; Henry S. Carhart, College Physics, Boston, 1918, pp.201-202.

Vibration Microscope

Vibration Microscope #10644
Rudolph Koenig, Paris
An electrically driven tuning fork has a microscope mounted on it to view the vibration of a string attached to the fork.
Reference: Gerard L’E Turner, The Practice of Science in the Nineteenth Century: Teaching and Research Apparatus in the Teyler Museum, Haarlem, the Netherlands, 1996, p.127; Max Kohl Catalogue No. 50 (c.1911) p.454.

Sensitive Flame Burner

Sensitive Flame Burner #10442
Max Kohl, Chemnitz
A gas jet is positioned below a metal screen and a flame is lit above the screen. The flame is very sensitive to sound waves entering the space around the jet through a funnel (missing) and fluctuations of the flame are related to the shape of the sound wave.
Reference: Max Kohl Catalogue No.50 (c.1911) p.418.

Singing Flame

Singing Flame #10319
Max Kohl, Chemnitz
Flames from gas jets inside four glass tubes (one broken) produce random noise with many frequencies. The tubes resonate only at certain frequencies thus amplifying the sound at those frequencies.
References: Gerard L’E Turner, The Practice of Science in the Nineteenth Century: Teaching and Research Apparatus in the Teyler Museum, Haarlem, the Netherlands, 1996, p.129; Max Kohl Catalogue No. 100 (c.1927) p.359.

Wave Machine

Wave Machine #10008
Max Kohl, Chemnitz
As the crank is turned, a wave trough moves horizontally, making the pins resting on it rise and fall, illustrating transverse wave motion. This particular model, designed by Friedrich Fessel and Julius Plücker, could also show double refraction. This results when two components of a wave, polarized at right angles to each other, are propagated at different speeds. This is accomplished in the wave machine by combining the waves produced by two troughs that move at different rates derived from different gearing ratios.
Reference: Max Kohl Catalogue No.100 (c.1927) p.352.

Sound Interference Tube

Sound Interference Tube #10009
Max Kohl, Chemnitz
Sound, e.g. from a tuning fork, enters the tube, is split into two branches, and is reunited at the other side where it is detected. The length of one branch may be varied by sliding out the tubes in somewhat the same way as in a trombone to show constructive and destructive interference of the two sound waves as their relative phases vary.
Reference: Max Kohl Catalogue No.50 (c.1911) p.461.

Hertzian Wave Machine

Hertzian Wave Machine #10681
Max Kohl, Chemnitz
Silvanus Thompson devised this wave machine to demonstrate the electromagnetic waves predicted by James Clerk Maxwell and first produced by Heinrich Hertz in the 1880s and 90s. By rotating part of the support for the swinging balls, the wave can be converted from longitudinal to transverse. Parts of the original apparatus, now lost, acted as the "transmitter" and "receiver" of the waves.
Reference: Max Kohl Catalogue No. 100 (c.1927) p.349.

Helmholtz’s Double Siren and Electric Motor

Helmholtz’s Double Siren and Electric Motor #10091 and 10113
The two sirens rotate on a common axle and therefore at the same rate, but the number of holes in the siren disks can be changed to produce two sounds of frequencies that are in exactly known ratios such as 2:1, 3:2, 4:3, etc., corresponding to familiar musical intervals. The instrument was used by John Tyndall in his famous lectures and described in detail in his book on sound. A motor with a complex governor system drives the sirens.
References: Max Kohl Catalogue No. 100 (c.1927) p.354-55; John Tyndall, Sound, New York, 1901, pp.411-18.

Apparatus to demonstrate vibrations of liquid films

Apparatus to demonstrate vibrations of liquid films
Max Kohl, Berlin
A cylindrical cell mounted on a low cast iron tripod has a tube on the side to admit sound. One of three plates with apertures (circular, square, or triangular) is placed on top and a liquid film is formed across the aperture. When sound from, say, a tuning fork enters the cell through the tube, two-dimensional standing waves form in the membrane. The apparatus, proposed by Rudolph Koenig, was made by him and also later by Max Kohl.
Reference: Rudolf Koenig, Catalogue des Appareils d'Acoustique, Paris 1889; Max Kohl Price List #50, Vol. II, pg. 443. Thanks to Paolo Brenni for identifying this instrument.