Poor Line of Position Computer Circular Slide Rule Retailed by Negus
date: label: date made
content: 1914-1918
name: label: maker
content: Negus, T. S. & J. D.
notes: label: Description
content: This line of position computer, or mechanical navigator, is essentially a circular slide rule for determining one's location, either from morning or afternoon sightings for longitude or from the St. Hilaire method of finding the line of position. It has a circular black steel base, a green felt cushioning ring, an engraved brass disc, and a yellowed and warped celluloid disc. The metal and plastic arm that extends over the celluloid disc has a brass thumbscrew at the outer edge. The celluloid disc and arm can rotate together or independently.
label: Description
content: The brass disc is calibrated logarithmically in several concentric rings: from 80 to 0 degrees by minute in both directions (altitudes, adjusted by latitude and declination), from 0 to 500 by 1 (numbers), from 100/10/1 to 600/60/6 (logarithms), from 0 to 12 hours (hour angles), from 0 to 70 degrees by 1 X 2 (declinations), from I to XII by I (hour angles), and from 0 to 180 degrees (altitudes and azimuths).
label: Description
content: The computer is housed in a square wooden case (lock broken and handle missing) with doors that open from the top. It appears to be impossible to remove the computer from the case. Two copies of an instructional flyer are stored separately (MA.320413.1). These describe the computer as built in two sizes, for military aircraft and for battleships. It is not clear, though, whether the computer was able to place a ship close enough to its actual position (within 0.5 to 9.6 miles, according to the examples in the flyer) to be of use for military purposes around the time of World War I. The scarcity of surviving examples suggests the government and general public had little interest in the instrument. Indeed, aviators preferred inspection tables over slide rules for navigation.
label: Description
content: The instrument is engraved near the center: LINE OF POSITION COMPUTER (/) DESIGNED BY (/) CHAS. LANE POOR (/) NEW YORK, U.S.A. (/) PATENT APPLIED FOR.
label: Description
content: This computer was sold by the nautical instrument firm founded in 1850 by T. S. & J. D. Negus of New York City. It was invented between 1914 and 1918 (the date of his patent application) by Charles Lane Poor (1866–1951), who earned a Ph.D. under Simon Newcomb at The Johns Hopkins University in 1892. Poor taught at Johns Hopkins until 1899, when he took over his father’s print works in New Jersey. From 1903 to 1944, Poor was professor of celestial mechanics at Columbia University. He was a critic of Einstein’s theory of relativity and an avid yachtsman.
label: Description
content: References: Charles Lane Poor, "Navigation Instrument" (U.S. Patent 1,308,748 issued July 1, 1919); Charles Lane Poor, <i>Simplified Navigation for Ships and Aircraft</i> (New York: The Century Co., 1918); Richard Berendzen and Richard Hart, "Poor, Charles Lane," <i>Dictionary of Scientific Biography</i> xi:83–84; <i>National Cyclopaedia of American Biography</i> xxxviii:614; Ronald van Riet, "Position Line Slide Rules: Bygrave and Höhenrechenschieber," https://sites.google.com/site/sliderulesite/position-line-slide-rules.
label: Location
content: Currently not on view
place: label: place made
content: United States: New York, New York City
topic: label: Subject
content: Mathematics
label: Subject
content: Rule, Calculating
label: Subject
content: Navigation
label: Subject
content: Navigation, Aeronautical
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Science & Mathematics
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content: Slide Rules
creditLine: label: Credit Line
content: Gift of Ferdinand Oberthol, Pupin Physics Laboratory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.320413
label: catalog number
content: 320413
label: accession number
content: 242377
objectType: label: Object Name
content: slide rule
physicalDescription: label: Physical Description
content: hardwood (case material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: celluloid (part material)
label: Physical Description
content: metal (part material)
label: Measurements
content: overall: 42.5 cm x 42.5 cm x 5.7 cm x 42.5 cm; 16 23/32 in x 16 23/32 in x 2 1/4 in x 16 23/32 in