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Correspondence

Letter from Linus Pauling to Irvin Stewart. April 5, 1939.
Pauling writes to submit his request for a grant from the Committee on Scientific Aids to Learning for the construction of a Fourier calculator. He explains that current methods for calculating Fourier series are both tedious and slow, and that a calculator would allow for research to continue at a rapid place. The Caltech laboratories would use the device, designed by a professional instrument maker, in connection with the determination of crystal structures via x-ray methods.

Transcript

Copy of report filed under "PROGRESS OF RESEARCH REPORTS"

April 5, 1939

Dr. Irvin Stewart, Director

Committee on Scientific Aids to Learning

41 East 42nd Street

New York, New York

During the past few months the situation with respect to the Fourier Calculator which we hope to construct has changed greatly. The plans initially made for a Fourier Synthesizer of rather conventional design were unsatisfactory, as pointed out by Dr. Fry.

About two months ago Dr. C. A. Beevers, of Liverpool, wrote to us suggesting that a Fourier Calculator could be designed for crystal structure use along the lines of the Beevers-Lipson strips, which are now being used successfully here and in other laboratories. Mr. Philip A. Shaffer has acted on this suggestion and has made a preliminary design of a Fourier Calculator of the new type, described on the accompanying pages. This calculator seems to be extremely promising. We had estimated that a two-dimensional Fourier synthesis, which now requires from four days to a week for its calculation with use of the Beevers-Lipson strips, could be carried out with a harmonic synthesizer drawing curves in from twelve to sixteen hours. The new Fourier Calculator would, it is estimated, turn out the same job in from one to two hours, an improvement over present methods by a factor of about 50. This improvement in the crystal structure technique should be of extremely great value, permitting an attack to be made on crystals of highly complex structure, such as those of proteins and other substances of biological importance.

Since Mr. Shaffer has not had experience in instrument design, we have made arrangements with the Observatory Council of California Institute for an expert instrument designer, Mr. Michael Karelits, to devote part of his time to the detailed design of the Fourier Calculator this Spring.

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Mr. Karelitz is employed permanently as an instrument designer in connection with the construction of instruments for use with the 200 inch telescope at Mt. Palomar. I believe that we can be sure that a satisfactory detailed design of the instrument will be prepared under Mr. Karelitz's direction. The designing process is now well under way, and we expect the design to be completed within two months.

I should like very much to have the construction of the Fourier Calculator begun immediately on completion of the design and completed if possible during the summer. Mr. Karelitz estimates that the cost of construction will be about $2000, aside from the cost of the design. From previous experience with the construction of apparatus, I would expect that the machine might accordingly cost between $2000 and $2500. Our research funds permit us to bear the cost of the design and a portion of the cost of construction, but not the entire cost.

I accordingly apply to your Committee for a grant of $2000 to be used for the construction of a Fourier Calculator for use in connection with the determination of the structure of crystals by x-ray methods.

I wish again to point out that this calculator would be used very extensively. There are in these Laboratories at present three staff members (Pauling, Sturdivant, Helmholz), four post-Ph.D. fellows (Corey, Hughes, Levy, Weinbaum), and several graduate students devoting their research efforts largely to crystal structure work.

Respectfully yours,

Linus Pauling

LP/jr

Enclosure

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