On June 15, 1944, Rest furnished to a representative of Soviet intelligence (M.G.B.), Part III of a document now identified as MSN-12. This document dated June 6, 1944, is on file with the Atomic Energy Commission and is entitled "Fluctuations and the Efficiency of a Diffusion Plant," and Part III specifically refers to "The Effect of Fluctuations in the Flow of N2." The designation MSN stands for documents prepared by British scientists who were in New York City working on Atomic Energy research. The author of this document is K. Fuchs, who is actually Emil Julius Klaus Fuchs, who is usually known as Karl Fuchs. He is a top ranking British Atomic scientist.
Information available concerning Rest indicated that he was a British scientist, inasmuch as he had also furnished to the Soviet Intelligence information concerning British participation in the Atomic Energy development. It was also indicated that he had a sister in the United States. There are indications that Rest was actually the author of the document.
Emil Julius Klaus Fuchs also known as Karl Fuchs, was born December 19, 1911, at Russelsheim, Germany. His father, Emil Fuchs was born May 13, 1874, and was a professor in Germany. Emil Julius Klaus Fuchs entered the United Kingdom in 1933, and from 1941 to 1943, was a medical physicist at the University of Birmingham, England. In November 1943, he was designated by the British Government to come to the United States as a part of the British Atomic Energy Commission. He arrived at New York City on December 3, 1943, and went to Los Alamos in August 1944. While in the United States, Fuchs worked with a group of British scientists in the period of March to June 1944, on the development of diffusional operational processes working particularly with the Kellex Corporation, which was working under the Manhattan Engineering District. Fuchs left for England from Montreal, Canada, on June 28, 1946.
In November 1947, Fuchs was back in the United States and visiting the Chicago Operations Office of the Atomic Energy Commission. At that time, he attended discussions regarding unclassified and declassified aspects of neutron spectroscopy. He also participated in declassification conferences which were being held between the United States, Great Britain and Canada. Fuchs is presently the senior research worker at the Atomic Energy Commission project at Harwell, England.
Fuchs has a sister, Kristal Fuchs Heineman, who prior to January 1941, resided at 55 Carver Road, Watertown, Massachusetts. From approximately 1941, until about 1945, she resided with her husband, Robert Block Heineman at 144 Lakeview Avenue, Cambridge, Massachusetts. They presently reside at 94 Lakeview Avenue, Cambridge, Massachusetts. Robert Block Heineman has been reliably reported as a member of the Communist Party, United States of America in 1947.
The address book of Israel Halperin implicated in the Canadian Espionage network contained the following: "Klaus Fuchs, Asst. to M. Born, 84 Grange Lane, University of Edinburgh, Scotland Camp (possibly comp) N.—Camp L., Internment Operations—Kristal Heineman, 55 Carvel Road, Watertown." The phrase Camp L is encircled.
In addition to the foregoing a captured German document prepared presumably by German Counter Intelligence and which relates to Communist Party members in Germany contains the following:
"Klaus Fuchs, student of philosophy, December 29, 1911, Russelsheim, RSHA-IVA2, Gestapo Field Office Kiel.
"Gerhard Fuchs, October 30, 1909, Russelsheim, student RSHA-IVA2, Gestapo Field Office Kiel."
It is to be noted that Gerhard Fuchs is the brother of Emil Julius Klaus Fuchs.
In connection with Rest, who furnished the document MSN-12 and who is thought to be Emil Julius Klaus Fuchs, it is also known that Rest's sister was a contact of Gus (Goose), who has presumably a scientific background. You will recall, Gus contemplated preparing a work on the production method with respect to the thermal diffusion of gases.
You will also recall, Gus, who has not been identified, was also a contact of Abraham Brothman, a Consulting Engineer in New York City, who furnished espionage information to Elizabeth Bentley in 1940.
It is thought that Gus may possibly be identical with Arthur Phineas Weber, who is presently an employee of the Kellex Corporation which is engaged in work under the Atomic Energy Commission. Weber was born March 10, 1920, in Brooklyn, New York, and is a chemical engineer. From 1941 to 1942, he worked with Brothman for the Henderick Manufacturing Company. From June 1942 to June 1944, he worked with Brothman in the Chemurgy Design Corporation, and according to some information during a part of this period he was also working for the Kellex Corporation. Weber lists employment with Kellex Corporation as a chemical engineer from July 1944 to March 29, 1946, and again from April 8, 1946, to the present. It should be noted that the Kellex Corporation was closely working in 1944 with the British Scientist group which included Fuchs.
Robert Louis Benson and Michael Warner, eds., Venona: Soviet Espionage and the American Response, 1939–1957 (Washington, DC: National Security Agency: Central Intelligence Agency, 1996), 141–143. Reprinted in Robert Louis Benson and Michael Warner, eds., Venona: Soviet Espionage and the American Response, 1939–1957 (Laguna Hills, CA: Aegean Park Press, 1997). .