A New Dimension For the Healing Arts

“One day the United States will have a National Museum of science, engineering, and industry, as most large nations have.” This was the prediction made in 1946 by the director of the U.S. National Museum, Mr. Frank A. Taylor, then curator of the Division of Engineering. [19] It was in 1963, that the new $36,000,000 building of the Museum of History and Technology was completed, and opened to the public in 1964. The offices of the Division of Medical Sciences as well as the reference and study collections were moved to the fifth floor of the new building. The exhibits, however, will be displayed in the gallery at the southwest corner of the first floor. These exhibits, it is hoped, will show a new dimension and an unprecedented approach in displaying the development of the healing arts throughout the ages and the instruments and equipment associated with health professions. They also present the expanding objectives and plans of the Division’s growth as an integral part of the Smithsonian Institution. Conveniently, the exhibits form four, closely connected halls in one large gallery which will be open to the public in the summers of 1965 to 1966.

1. The Hall of Health displays models and graphic and historical exhibit materials to demonstrate the function of the various healthy organs of the human body. The main topics emphasized are: embryology and childbirth; tooth structure; the heart and blood circulation; respiration; the endocrine glands; kidneys and the urinary-excretory system; the brain and the nervous system; the ear; and vision and the use of eyeglasses.

The most appreciated exhibit of all in this Hall is the “transparent woman” figure which rotates, automatically, every 15 minutes with a recorded message describing the function of each major organ of the body at the same time that the organ is electronically lighted, so that the viewer can see its place in the body.

Exhibits on the development of dentistry and dental surgery will display examples of tooth-filling and extracting tools, drilling apparatus from the early hand and foot engines to the first ultrasonic cutting instrument (1954), and the original contra-angle, hydraulic and air-turbine handpiece model [20] which revolutionized the field of instrumentation for dental surgery (with speeds of 200,000 to 400,000 rpm). This hydraulic turbine of Dr. Robert J. Nelson and associates of the National Bureau of Standards set the design pattern for the remarkable and successful high-speed, air-turbine handpiece developed by Paul H. Tanner and Oscar P. Nagel of the U.S. Naval Dental School in 1956. Also underway is the reconstruction of the offices of famous dentists such as G. V. Black and the father of American orthodontia, Edward H. Angle, using their original equipment and instruments. In addition, an exhibit is planned to include x-ray tubes and the electric dental engine, the first to be operated in a human mouth by the pioneer dentist on dental skiagraphy, Charles E. Kells (1856-1928). [21]

3. The Hall of Pharmaceutical History will feature exhibits on the reconstruction of two pharmacy shops: an 18th-century apothecary shop, originally from Germany, with a very elegant collection of drug jars, decorated medicinal bottles, balances, mortars and pestles, and other tools and documents pertaining to the apothecary art, and a late 19th-century American drugstore with shelves filled with patent medicines and drug containers of various sizes and shapes. The window will also feature symbols of pharmacy and beautiful show globes. Displays will show the development of antibiotics and the early tools used in the manufacture of the so-called “miracle drugs,” including a mold from Sir Alexander Fleming, the discoverer of penicillin. In addition, a platform will be reconstructed to display a variety of pharmaceutical apparatus used in the preparation and manufacture of drugs, such as tablet and capsule machines and drug mills and percolators. Recently, with the assistance of Professor Glenn Sonnedecker, the Division acquired a fine collection of pharmaceutical equipment and devices from the School of Pharmacy of the University of Wisconsin.

BIBLIOGRAPHY

Contributions from
The Museum of History and Technology:
Paper 44


Development of Gravity Pendulums in the 19th Century

GALILEO, HUYGENS, AND NEWTON  304

FIGURE OF THE EARTH  306

EARLY TYPES OF PENDULUMS  309

KATER’S CONVERTIBLE AND INVARIABLE PENDULUMS  314

REPSOLD-BESSEL REVERSIBLE PENDULUM  320

PEIRCE AND DEFFORGES INVARIABLE, REVERSIBLE PENDULUMS  327

VON STERNECK AND MENDENHALL PENDULUMS  331

ABSOLUTE VALUE OF GRAVITY AT POTSDAM  338

APPLICATION OF GRAVITY SURVEYS  342

SUMMARY  346

Victor F. Lenzen and
Robert P. Multhauf

DEVELOPMENT OF GRAVITY PENDULUMS
IN THE 19th CENTURY

The intensity of gravity, or the acceleration of a freely falling body, is an important physical quantity for the several physical sciences. The intensity of gravity determines the weight of a standard pound or kilogram as a standard or unit of force. In physical experiments, the force on a body may be measured by determining the weight of a known mass which serves to establish equilibrium against it. Thus, in the absolute determination of the ampere with a current balance, the force between two coils carrying current is balanced by the earth’s gravitational force upon a body of determinable mass. The intensity of gravity enters into determinations of the size of the earth from the angular velocity of the moon, its distance from the earth, and Newton’s inverse square law of gravitation and the laws of motion. Prediction of the motion of an artificial satellite requires an accurate knowledge of gravity for this astronomical problem.

The gravity field of the earth also provides data for a determination of the figure of the earth, or geoid, but for this problem of geodesy relative values of gravity are sufficient. If g is the intensity of gravity at some reference station, and Δg is the difference between intensities at two stations, the values of gravity in geodetic calculations enter as ratios (Δg)/g over the surface of the earth. Gravimetric investigations in conjunction with other forms of geophysical investigation, such as seismology, furnish data to test hypotheses concerning the internal structure of the earth.

Whether the intensity of gravity is sought in absolute or relative measure, the most widely used instrument for its determination since the creation of classical mechanics has been the pendulum. In recent decades, there have been invented gravity meters based upon the principle of the spring, and these instruments have made possible the rapid determination of relative values of gravity to a high degree of accuracy. The gravity meter, however, must be calibrated at stations where the absolute value of gravity has been determined by other means if absolute values are sought. For absolute determinations of gravity, the pendulum historically has been the principal instrument employed. Although alternative methods of determining absolute values of gravity are now in use, the pendulum retains its value for absolute determinations, and even retains it for relative determinations, as is exemplified by the Cambridge Pendulum Apparatus and that of the Dominion Observatory at Ottawa, Ontario.

The pendulums employed for absolute or relative determinations of gravity have been of two basic types. The first form of pendulum used as a physical instrument consisted of a weight suspended by a fiber, cord, or fine wire, the upper end of which was attached to a fixed support. Such a pendulum may be called a “simple” pendulum; the enclosure of the word simple by quotation marks is to indicate that such a pendulum is an approximation to a simple, or mathematical pendulum, a conceptual object which consists of a mass-point suspended by a weightless inextensible cord. If l is the length of the simple pendulum, the time of swing (half-period in the sense of physics) for vibrations of infinitely small amplitude, as derived from Newton’s laws of motion and the hypothesis that weight is proportional to mass, is T = π√(l/g).

The second form of pendulum is the compound, or physical, pendulum. It consists of an extended solid body which vibrates about a fixed axis under the action of the weight of the body. A compound pendulum may be constituted to oscillate about one axis only, in which case it is nonreversible and applicable only for relative measurements. Or a compound pendulum may be constituted to oscillate about two axes, in which case it is reversible (or “convertible”) and may be used to determine absolute values of gravity. Capt. Henry Kater, F.R.S., during the years 1817-1818 was the first to design, construct, and use a compound pendulum for the absolute determination of gravity. He constructed a convertible pendulum with two knife edges and with it determined the absolute value of gravity at the house of Henry Browne, F.R.S., in Portland Place, London. He then constructed a similar compound pendulum with only one knife edge, and swung it to determine relative values of gravity at a number of stations in the British Isles. The 19th century witnessed the development of the theory and practice of observations with pendulums for the determination of absolute and relative values of gravity.

Galileo, Huygens, and Newton

The pendulum has been both an objective and an instrument of physical investigation since the foundations of classical mechanics were fashioned in the 17th century. [1] It is tradition that the youthful Galileo discovered that the period of oscillation of a pendulum is constant by observations of the swings of the great lamp suspended from the ceiling in the cathedral of Pisa. [2] The lamp was only a rough approximation to a simple pendulum, but Galileo later performed more accurate experiments with a “simple” pendulum which consisted of a heavy ball suspended by a cord. In an experiment designed to confirm his laws of falling bodies, Galileo lifted the ball to the level of a given altitude and released it. The ball ascended to the same level on the other side of the vertical equilibrium position and thereby confirmed a prediction from the laws. Galileo also discovered that the period of vibration of a “simple” pendulum varies as the square root of its length, a result which is expressed by the formula for the time of swing of the ideal simple pendulum. He also used a pendulum to measure lapse of time, and he designed a pendulum clock. Galileo’s experimental results are important historically, but have required correction in the light of subsequent measurements of greater precision.

Mersenne in 1644 made the first determination of the length of the seconds pendulum, [3] that is, the length of a simple pendulum that beats seconds (half-period in the sense of physics). Subsequently, he proposed the problem to determine the length of the simple pendulum equivalent in period to a given compound pendulum. This problem was solved by Huygens, who in his famous work Horologium oscillatorium … (1673) set forth the theory of the compound pendulum. [4]

Huygens derived a theorem which has provided the basis for the employment of the reversible compound pendulum for the absolute determination of the intensity of gravity. The theorem is that a given compound pendulum possesses conjugate points on opposite sides of the center of gravity; about these points, the periods of oscillation are the same. For each of these points as center of suspension the other point is the center of oscillation, and the distance between them is the length of the equivalent simple pendulum. Earlier, in 1657, Huygens independently had invented and patented the pendulum clock, which rapidly came into use for the measurement of time. Huygens also created the theory of centripetal force which made it possible to calculate the effect of the rotation of the earth upon the observed value of gravity.

The theory of the gravity field of the earth was founded upon the laws of motion and the law of gravitation by Isaac Newton in his famous Principia (1687). It follows from the Newtonian theory of gravitation that the acceleration of gravity as determined on the surface of the earth is the resultant of two factors: the principal factor is the gravitational attraction of the earth upon bodies, and the subsidiary factor is the effect of the rotation of the earth. A body at rest on the surface of the earth requires some of the gravitational attraction for the centripetal acceleration of the body as it is carried in a circle with constant speed by the rotation of the earth about its axis. If the rotating earth is used as a frame of reference, the effect of the rotation is expressed as a centrifugal force which acts to diminish the observed intensity of gravity.