Pickett N15-T Hydraulic Duplex Slide Rule for Georgia Iron Works

<< >>
From the 1650s people have devised special-purpose slide rules for tasks such as carpentry and tax collection. In 1961 Danforth (Danny) W. Hagler of the Georgia Iron Works Company in Augusta, Ga., designed this slide rule to replace the 100-page notebook of graphs carried by each GIW engineer. GIW also distributed the rule to customers to assist with ordering and operating pumps and pipelines. Pickett & Eckel, the California slide rule manufacturer, assisted with the design and produced the slide rules. For Pickett company history, see 1998.0119.02 and 2000.0203.01.
This ten-inch, two-sided white aluminum instrument has metal endpieces and a nylon cursor with white plastic edges. The front has logarithmic scales for calculating the kinetic energy and flow rate of a liquid or slurry moving through a pipeline. The top of the base is marked: HYDRAULIC SLIDE RULE (/) GEORGIA IRON WORKS CO. (/) EST. 1891 (/) AUGUSTA GEORGIA. The left end of the slide has a GIW logo. The right end of the slide has the triangular Pickett logo used between 1958 and 1962 and is marked: 338. The bottom of the base is marked: DESIGNED BY D. W. HAGLER.
The back has logarithmic scales for determining the head produced by a pump, impeller peripheral speed, brake horsepower, and specific speed. Standard C and D scales were added around 1969. The right end of the slide is marked: PICKETT (/) MODEL N 15-T (/) 337. The rule fits in an orange leather case with a belt loop. The front of the case is marked: HYDRAULIC SLIDE RULE (/) GIW (/) D. W. HAGLER (/) Pickett. The case fits inside a redwood box.
This particular rule was Hagler's personal example of the instrument in production. GIW was his family's business, and his brother, Tom, wrote an instruction manual for the rule (2009.0100.02). Hagler went on to work on computer software for production control. He sold his interest in GIW in 1986.
References: Helen Callahan, Georgia Iron Works: The First 100 Years (Columbia, S.C.: The R. L. Bryan Company, [1991]), 46–49; Michael V. Konshak, "Developing the Georgia Iron Works Hydraulic Slide Rule: Negotiating with Pickett & Eckel to Make a Special Slide Rule," Journal of the Oughtred Society 19, no. 2 (2010): 33–37; accession file.
Currently not on view
date made
date received
Pickett & Eckel, Incorporated
place made
United States: California, Alhambra
Physical Description
aluminum (overall material)
plastic (cursor material)
leather (case material)
wood (case material)
box: 6.5 cm x 35.5 cm x 10.5 cm; 2 9/16 in x 14 in x 4 1/8 in
ID Number
accession number
catalog number
Credit Line
Gift of Danforth W. Hagler
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History


Add a comment about this object