Gurley Cox's Stadia Computer Circular Slide Rule
date: label: date made
content: after 1899
name: label: maker
content: W. & L. E. Gurley
notes: label: Description
content: Some slide rules reveal transformations in materials. A later version of this paper circular slide rule was made from celluloid (1987.0221.02). Both were designed to reduce data obtained with a surveyor's transit.
label: Description
content: On the base, just outside the disc, is a logarithmic scale for readings of a stadia rod used with a transit telescope, in feet. The edge of the disc has two scales involving functions of angles. One scale allows for multiplying the stadia reading by 1/2 sin 2 A, where A is the vertical angle of the transit telescope. This multiplication gives the difference in elevation of the transit and the stadia rod, in feet. The second scale represents multiplying the stadia reading by the square of the cosine of A, to find the horizontal distance of the rod in feet. The instrument bears a copyright date of 1899. Compare this instrument to Webb’s stadia rule (333636) as well as to 1977.1141.41 and 2001.0282.01.
label: Description
content: The slide rule has a cloth-covered cardboard cover. Pasted on the inside of the cover is an image of the Light Mountain Transit sold by W. & L. E. Gurley of Troy, N.Y., from 1897 to 1908. The image of the transit in the 1910 Gurley catalog is different, but it is not the same as the image on rule 1987.0221.02. Cox’s stadia computer is not mentioned in any of these catalogs; the device was probably given away as a promotional item.
label: Description
content: In 1904, W. M. Beaman, a topographer in the U.S. Geological Survey, devised the “Beaman stadia arc,” a transit attachment that obviated the need for separate computing rules. Beaman obtained a patent for his instrument in 1906, and it was offered in Gurley catalogs from at least 1908.
label: Description
content: References: W. & L. E. Gurley, <i>A Manual of the Principal Instruments Used in American Engineering and Surveying</i>, 42nd ed. (Troy, N.Y., 1908), 62–63; Florian Cajori, "A Stadia Slide-Rule," <i>Engineering News</i> 43 (April 5, 1900): 232; Richard Smith Hughes, "Stadia or Tacheometric Slide Rules, Part II," <i>Journal of the Oughtred Society</i> 16, no. 2 (2007): 32–41.
label: Location
content: Currently not on view
place: label: place made
content: United States: New York, Troy
topic: label: Subject
content: Rule, Calculating
label: Subject
content: Engineering
label: Subject
content: Surveying
label: Subject
content: Mathematics
setName: label: See more items in
content: Medicine and Science: Mathematics
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content: Science & Mathematics
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content: Slide Rules
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1987.0221.01
label: accession number
content: 1987.0221
label: catalog number
content: 1987.0221.01
objectType: label: Object Name
content: slide rule
physicalDescription: label: Physical Description
content: paper (overall material)
label: Physical Description
content: cloth (case material)
label: Measurements
content: overall: .6 cm x 16.8 cm x 16.5 cm; 1/4 in x 6 5/8 in x 6 1/2 in