Selected frequencies from this precision station are amplified and may be transmitted to all parts of the three buildings. These frequencies, when desired, may also be used as master control of the laboratory radio transmitting sets. Another unit, a 1000-cycle master oscillator is used to supply 1000-cycle current to student laboratories and researches not requiring extreme precision. This oscillator is controlled in frequency to one part in 100,000 by a thermostated magnetostriction rod.

Professor Pierce's Work

Professor George W. Pierce has been one of the pioneers in the work on quartz-oscillators and magnetostriction rods which makes possible these measurements of frequency. His work has been with mechanical and electrical oscillations and their combined effect upon electric circuits. Apparatus containing these developments is used as the basis of frequency measurements in all modern radio broadcasting applications.

For fifty years there has been knowledge of the electrical effect due to mechanical operation on quartz. In the 1890's, the Curie family worked on this problem. Here and abroad during the War, work on vibration of quartz plates by electrical means was carried on. They were used for depth finding by high frequency of sound reflected from the ocean bottom. Quartz vibrators were used for production and reception. Professor Pierce, and others, also found at this time that the quartz crystal was useful in stabilizing electrical oscillations.

Since any mechanical vibration is sharply resonant, and better than the best electric circuits which can be built Professor Pierce has also been at work on magnetostriction rods, usually an alloy of nickel and steel, used, experimentally, as a source of air waves, similar to sound waves, but above audible limit, especially in the range: 30,000 to 50,000 cycles. Such waves can be focused, confined to narrow beams like those from a searchlight. Both the quartz crystal and magnetostriction rod are being worked on for communication purposes, and are also used to study the elastic properties of materials.

Edwin H. Hall, Professor Emeritus, continues to carry on experiments on conduction in metals. In the new building he has set up new devices for studying these problems.

Spectra and Sound

Professor Frederick A. Saunders has done his main work in spectroscopy; he was a pioneer in the study of series spectra long before the importance of this subject was generally recognized. He is also an authority in the domain of sound from the theoretical, practical and aesthetic points of view. In this field he has been the successor at Harvard of Professor Sabine.

Professor Emory L. Chaffe has done his principal work in the realm of electric oscillation and electric waves, with special reference to vacuum-tube phenomena. He has also devoted himself to biophysical problems, notably to a study of the electric response of the retina when stimulated by light.

Experiments on conduction in gases are being carried on by Professor Otto Oldenberg, who came to Harvard in 1930. His special field is the excitation of atoms and molecules studied largely by spectroscopic methods. He has also organized a course of fundamental experiments in atomic physics for graduate students.

New Grating Room

Assistant Professor F. H. Crawford is engaged in a study of the light emitted by the atoms and molecules of a gas under the influence of various types of electrical discharge. He is in charge of the new grating room. In an outer room ample space is available to accomodate apparatus used in the preliminary study of spectroscopic questions. Inside the grating room, the space occupied by the twenty-one foot concave grating is seperated from the rest of the room in such a way that the temperature within it may be kept constant. A circular bench of concrete is provided, which carries the supports for the holders of the photographic plates, upon which the lines of the spectrum are reproduced for further study.

Professor Theodore Lyman is Director of the Jefferson Laboratory. His field of research is the study of light of extremely short wave length.

Part of the time of Professor William Duane is spent at the Huntington Hospital, where he devotes himself to the use of X-rays and the radiation from radioactive substances in the treatment of maligant disease; part is devoted to research in pure science in the laboratories at Cambridge. His title is that of Professor of Biophysics.

X-ray Laboratory and Vault