Measuring & Mapping

Vernier Compass

Where, how far, and how much? People have invented an astonishing array of devices to answer seemingly simple questions like these. Measuring and mapping objects in the Museum's collections include the instruments of the famous—Thomas Jefferson's thermometer and a pocket compass used by Meriwether Lewis and William Clark on their expedition across the American West. A timing device was part of the pioneering motion studies of Eadweard Muybridge in the late 1800s. Time measurement is represented in clocks from simple sundials to precise chronometers for mapping, surveying, and finding longitude. Everyday objects tell part of the story, too, from tape measures and electrical meters to more than 300 scales to measure food and drink. Maps of many kinds fill out the collections, from railroad surveys to star charts.

Date: 1940s

Marine Compass Co. Dry Card Compass

This compass has a metal bowl gimbal mounted in a wooden box. It was used on a lifeboat of the SS Alcoa Mariner, an American freighter torpedoed by a German submarine in September 1942. Frank B. Hodges, a sailor on the Alcoa Mariner, gave it to the Smithsonian.
Description
This compass has a metal bowl gimbal mounted in a wooden box. It was used on a lifeboat of the SS Alcoa Mariner, an American freighter torpedoed by a German submarine in September 1942. Frank B. Hodges, a sailor on the Alcoa Mariner, gave it to the Smithsonian. The inscriptions read "M. C. CO." and "ALCOA MARINER." The former refers to the Marine Compass Company, a firm that was established in Hanover, Massachusetts, in 1910. The owners of this firm purchased E. S. Ritchie & Son in 1951.
Location
Currently not on view
date made
ca 1940
maker
Marine Compass Company
ID Number
1990.0577.01
accession number
1990.0577
catalog number
1990.0577.01

Nier Mass Spectrograph

Background on Nier Mass Spectrograph; object id no. 1990.0446.01; catalog no. N-09567This object consists of the following three components: ion source with oven and acceleration electrode; semicircular glass vacuum chamber; ion collector with two plates.
Description
Background on Nier Mass Spectrograph; object id no. 1990.0446.01; catalog no. N-09567
This object consists of the following three components: ion source with oven and acceleration electrode; semicircular glass vacuum chamber; ion collector with two plates. The original device included an electromagnet, which is not part of this accession.
In 1939, as political tensions in Europe increased, American physicists learned of an astonishing discovery: the nucleus of the uranium atom can be split, causing the release of an immense amount of energy. Given the prospects of war, the discovery was just as worrying as it was intellectually exciting. Could the Germans use it to develop an atomic bomb?
The Americans realized that they had to determine whether a bomb was physically possible. Uranium consists mostly of the isotope U-238, with less than 1% of U-235. Theoreticians predicted that it was the nuclei of the rare U-235 isotope that undergo fission, the U-238 being inactive. To test this prediction, it was necessary to separate the two isotopes, but it would be difficult to do this since they are chemically identical.
Alfred Nier, a young physicist at the University of Minnesota, was one of the few people in the world with the expertise to carry out the separation. He used a physical technique that took advantage of the small difference in mass of the two isotopes. To separate and collect small quantities of them, he employed a mass spectrometer technique that he first developed starting in about 1937 for measurement of relative abundance of isotopes throughout the periodic table. (The basic principles of the mass spectrometer are described below.)
As a measure of the great importance of his work, in October 1939, Nier received a letter from eminent physicist Enrico Fermi, then at Columbia University, expressing great interest in whether, and how, the separation was progressing. Motivated by such urging, by late February 1940, Nier was able to produce two tiny samples of separated U-235 and U-238, which he provided to his collaborators at Columbia University, a team headed by John R. Dunning of Columbia. The Dunning team was using the cyclotron at the University in numerous studies to follow up on the news from Europe the year before on the fission of the uranium atom. In March 1940, with the samples provided by Nier, the team used neutrons produced by a proton beam from the cyclotron to show that it was the comparatively rare uranium-235 isotope that was the most readily fissile component, and not the abundant uranium-238.
The fission prediction was verified. The Nier-Dunning group remarked, "These experiments emphasize the importance of uranium isotope separation on a larger scale for the investigation of chain reaction possibilities in uranium" (reference: A.O. Nier et. al., Phys. Rev. 57, 546 (1940)). This proof that U-235 was the fissile uranium isotope opened the way to the intense U.S. efforts under the Manhattan Project to develop an atomic bomb. (For details, see Nier’s reminiscences of mass spectrometry and The Manhattan Project at: http://pubs.acs.org/doi/pdf/10.1021/ed066p385).
The Dunning cyclotron is also in the Modern Physics Collection (object id no. 1978.1074.01; catalog no. N-09130), and it will be presented on the SI collections website in 2015. (Search for “Dunning Cyclotron” at http://collections.si.edu/search/)
The Nier mass spectrometer used to collect samples of U-235 and U-238 (object id no. 1990.0446.01)
Nier designed an apparatus based on the principle of the mass spectrometer, an instrument that he had been using to measure isotopic abundance ratios throughout the entire periodic table. As in most mass spectrometers of the time, his apparatus produced positive ions by the controlled bombardment of a gas (UBr˅4, generated in a tiny oven) by an electron beam. The ions were drawn from the ionizing region and moved into an analyzer, which used an electromagnet for the separation of the various masses. Usually, the ion currents of the separated masses were measured by means of an electrometer tube amplifier, but in this case the ions simply accumulated on two small metal plates set at the appropriate positions. Nier’s mass spectrometer required that the ions move in a semicircular path in a uniform magnetic field. The mass analyzer tube was accordingly mounted between the poles of an electromagnet that weighed two tons, and required a 5 kW generator with a stabilized output voltage to power it. (The magnet and generator were not collected by the Smithsonian.) The ion source oven, 180-degree analyzer tube, and isotope collection plates are seen in the photos of the Nier apparatus (see accompanying media file images for this object).
Basic principles of the mass spectrometer
When a charged particle, such as an ion, moves in a plane perpendicular to a magnetic field, it follows a circular path. The radius of the particle’s path is proportional to the product of its mass and velocity, and is inversely proportional to the product of its electrical charge and the magnetic field strength. A mass spectrometer consists of three components: an ion source, a mass analyzer, and a detector. The ion source converts a portion of the sample into ions. There is a wide variety of ionization techniques, depending on the phase (solid, liquid, gas) of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample and gives them a selected velocity. They then pass through the magnetic field (created by an electromagnet) of the mass analyzer. For a given magnetic field strength, the differences in mass-to-charge ratio of the ions result in corresponding differences in the curvature of their circular paths through the mass analyzer. This results in a spatial sorting of the ions exiting the analyzer. The detector records either the charge induced or the current produced when an ion passes by or hits a surface, thus providing data for calculating the abundance and mass of each isotope present in the sample. For a full description with a schematic diagram of a typical mass spectrometer, go to: http://www.chemguide.co.uk/analysis/masspec/howitworks.html
The Nier sector magnet mass spectrometer (not in Smithsonian Modern Physics Collection)
In 1940, during the time that Nier separated the uranium isotopes, he developed a mass spectrometer for routine isotope and gas analysis. An instrument was needed that did not use a 2-ton magnet, or required a 5 kW voltage-stabilized generator for providing the current in the magnet coils. Nier therefore developed the sector magnet spectrometer, in which a 60-degree sector magnet took the place of the much larger one needed to give a 180-degree deflection. The result was that a magnet weighing a few hundred pounds, and powered by several automobile storage batteries, took the place of the significantly larger and heavier magnet which required a multi-kW generator. Quoting Nier, “The analyzer makes use of the well-known theorem that if ions are sent into a homogeneous magnetic field between two V-shaped poles there is a focusing action, provided the source, apex of the V, and the collector lie along a straight line” (reference: A.O. Nier, Rev. Sci. Instr., 11, 212, (1940)). This design was to become the prototype for all subsequent magnetic deflection instruments, including hundreds used in the Manhattan Project.
Location
Currently not on view
Date made
ca 1940-02
associated person
Nier, Alfred O.
maker
Nier, Alfred O.
ID Number
1990.0446.01
accession number
1990.0446
catalog number
1990.0446.01

Felsenthal FAE-6 Set Square/Coordinate Scale

On one side, this 4-3/8" white plastic L-shaped square has scales along its inner edge for reducing yards to the representative fraction (R.F.) of 1:20,000, divided to twenties and numbered by 500s from 0 to 1,000. Scales along its outer edge are for reducing yards to R.F.
Description
On one side, this 4-3/8" white plastic L-shaped square has scales along its inner edge for reducing yards to the representative fraction (R.F.) of 1:20,000, divided to twenties and numbered by 500s from 0 to 1,000. Scales along its outer edge are for reducing yards to R.F. 1:62,500, divided to hundreds and numbered by thousands from 1,000 to 6,000. The end of one leg is marked: U.S.
The other side has scales along its inner edge for reducing meters to R.F. 1:25,000, divided to twenties and numbered by 500s from 0 to 1,500. Scales along its outer edge are for reducing meters to R.F. 1:50,000, divided to fifties and numbered by thousands from 1,000 to 5,000. The end of one leg is marked: U.S. The device, also known as a "coordinate scale," was used by soldiers to compare measurements to notations on a chart in order to aim weapons. Compare to 1977.1141.16. This example was also received with a duplicate square, but the second square was broken and discarded.
According to the accession file, this instrument was made for the U.S. Army by Felsenthal Instrument Company in 1945 as model number FAE-6. The company was the leading supplier of mathematical instruments to the U.S. Army Air Force and the U.S. Navy Bureau of Aeronautics, particularly during World War II (when the firm was known as G. Felsenthal & Sons). After the company ceased operations in approximately 1976, it provided a large sample of its products to the Smithsonian. The lack of any form of the firm's name on this instrument suggests it may actually have been made in the 1960s. For company history, see 1977.1141.02.
Location
Currently not on view
date made
ca 1945
maker
Felsenthal Instrument Co.
ID Number
1977.1141.17
catalog number
336401
accession number
1977.1141

Calculating Disc, Sherrill Compass Deviation Calculator, Felsenthal FAO-2

According to marks on this small plastic instrument, it was “furnished” by the Sherrill Research Corporation of Peru, Indiana, and copyrighted in 1944. At that time, Sherrill was making compasses for the U.S. military and sold this calculator to easily correct compass readings.
Description
According to marks on this small plastic instrument, it was “furnished” by the Sherrill Research Corporation of Peru, Indiana, and copyrighted in 1944. At that time, Sherrill was making compasses for the U.S. military and sold this calculator to easily correct compass readings. Instructions are on it.
According to a tag received with the object, Felsenthal made the instrument for the U.S. Army as the FAO-2 and sold it in 1943.
Location
Currently not on view
date made
ca 1943
ca 1944
maker
Felsenthal Instrument Co.
Felsenthal Instrument Co.
ID Number
1977.1141.15
catalog number
336399
accession number
1977.1141

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