Circular Slide Rules

An image of various slide rules from the collection of the Division of Medicine and Science at the National Museum of American History.

Slide rules that are round offer the length of a 10" rectangular slide rule in a pocket-sized (roughly 3.6") format, since the scales are on the circumference of circles. The scales are also continuous, so there is no need to make adjustments, such as folded and inverse scales, for results of calculations that go off the ends of the scales. Furthermore, these instruments are relatively easy to construct: the scales are printed on one or more disks, and the disks or a single disk and cursor are fastened together with a pin at the center. However, this simple construction is also not very durable, and so circular slide rules may get out of position and thus they lack accuracy, compared to linear slide rules with slides that move along carefully grooved channels.

This collection suggests the diverse appearances and functions of circular slide rules that were manufactured between the mid-19th and late 20th centuries. For example, before Mannheim-type linear slide rules became popular in the late 19th century, American inventors patented a variety of circular designs. Some circular slide rules were made to look like pocket watches, while others were intended to promote particular businesses—Whitehead & Hoag and Perrygraf were especially influential American manufacturers of promotional items. Inventors and makers such as Albert Sexton, Louis Ross, Claire Gilson, Norman Albree, and Ross Pickett wanted their circular slide rules to compete with linear instruments in the engineering and education markets. Other circular slide rules were designed specifically for surveying, such as stadia computers, or for navigation, such as Dalton instruments that may also be seen in the Smithsonian's exhibition, Time and Navigation. Even more specialized in purpose were slide rules for grading earthworks, determining the effects of nuclear bomb explosions, writing efficient computer programs, and betting on horse races.

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Concise Model 28 Circular Slide Rule

This white plastic circular slide rule was made by Concise Company, Ltd., of Tokyo, Japan, for Pan American Airlines. The base has a D scale, and there are C, CI, A, and K scales on a disc that rotates atop the base. A clear plastic indicator is pivoted at the center.
Description
This white plastic circular slide rule was made by Concise Company, Ltd., of Tokyo, Japan, for Pan American Airlines. The base has a D scale, and there are C, CI, A, and K scales on a disc that rotates atop the base. A clear plastic indicator is pivoted at the center. The center of the rotating disc is marked: CIRCULAR CONCISE SLIDE RULE (/) NO. 28 (/) MADE IN JAPAN.
The back of the object is light blue with a white logo of a globe and is marked: WORLD'S LARGEST AIR CARGO CARRIER (/) PAN AM (/) WORLD'S MOST EXPERIENCED AIRLINE. The instrument was received with a clear plastic sleeve, a black vinyl case, and an undated instruction manual. The case is marked: Concise (/) No. 28. In 1963, the rule was advertised as "a revolutionary new design concept."
Concise has specialized in circular slide rules, particularly for promotional distribution by other companies, since its founding in 1949. The company operated under the name Concise Co., Ltd., which appears on the instruction manual, from 1959 to 1966, hence the rough date assigned this slide rule. The donor, industrial engineer Richard Freeze, reported that he received the item as a promotional item distributed at a conference. For other Pan American promotional slide rules, see 1996.3029.01 and 1996.3029.02. For other slide rules by Concise, see 1985.0636.02, 1996.0141.01, and 2006.0173.01.
References: "Concise Corporate History," http://www.concise.co.jp/eng0731/history.html; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 105; advertisement, Civil Engineering 33 (February 1963): 84; accession file.
Location
Currently not on view
date made
1959-1966
distributor
Pan American Airlines
maker
Concise
ID Number
2003.0012.01
accession number
2003.0012
catalog number
2003.0012.01

Concise 270 Circular Slide Rule

This pocket-sized white plastic duplex circular slide rule has a clear plastic indicator that folds over the edge to serve both sides. It is held together with a metal pivot.
Description
This pocket-sized white plastic duplex circular slide rule has a clear plastic indicator that folds over the edge to serve both sides. It is held together with a metal pivot. The front base has L and D scales, with C, CI, A, and K scales on a sliding disc that fits inside the base. The center of the rotating disc is marked: CIRCULAR CONCISE SLIDE RULE (/) NO. 270 (/) MADE IN JAPAN. Near the center of both sides of the rule, the donor has scratched: SACK. The back base has DI and D scales, with S, T1, T2, and ST scales on the inset sliding disc.
The instrument was received with a clear plastic sleeve, a black vinyl case, and an undated instruction manual. The sleeve is marked: Concise (/) No. 270. As of 2012, Concise continues to manufacture plastic circular slide rules, including models 28N and 270N. The company operated under the name Concise Co., Ltd., which appears on the instruction manual, from 1959 to 1966. The donor, Michael Sackheim, reported that he purchased this rule for calculating during his school days but got little use out of it.
For other slide rules by Concise, see 1985.0636.02, 2003.0012.01, and 2006.0173.01.
References: "Concise Circular Slide Rule," http://www.concise.co.jp/eng0731/circle02.html#02; accession file.
Location
Currently not on view
date made
1959-1966
maker
Concise
ID Number
1996.0141.01
catalog number
1996.0141.01
accession number
1996.0141

Concise CTCS-552 Circular Slide Rule

This white plastic circular slide rule is on a rectangular base that has a 4-inch ruler on the left side and a 10-cm ruler on the right. The top of the base is marked: CONCISE (/) CONVERSION TABLES (/) AND CIRCULAR SLIDE RULE. The slide rule has a D scale along the outer rim.
Description
This white plastic circular slide rule is on a rectangular base that has a 4-inch ruler on the left side and a 10-cm ruler on the right. The top of the base is marked: CONCISE (/) CONVERSION TABLES (/) AND CIRCULAR SLIDE RULE. The slide rule has a D scale along the outer rim. A rotating disc fastened with a metal grommet has C, CI, L, A, and K scales. There is a clear plastic rotating indicator. The bottom of the base is marked: MODEL CTCS-552.
The back of the instrument has a table of the chemical elements, arranged in alphabetical order, and a chart for converting temperatures from Celsius to Fahrenheit. The bottom of the back is marked: MODEL CTCS-552 (/) SAMA & ETANI, INC. GROTON MASSACHUSETTS U.S.A. (/) MADE IN JAPAN BY CONCISE.
A rectangular plastic card fits inside a slot in the base. The card provides various physical constants and conversions for length, area, weight, volume, decimal equivalents to 64ths, velocity, gas constant values, flow rate, pressure, and energy. One edge of the card is marked: ©1966 CONCISE INTERNATIONAL CO., LTD. The instrument and an instruction manual providing contact information for Sama & Etani and copyrighted 1960 both fit in a black plastic case.
Domenick Sama and Kenzi Etani designed this style of slide rule and conversion card when they were students at the Massachusetts Institute of Technology in 1954. By the mid-1960s, Concise, a firm in Tokyo, Japan, was manufacturing the device for Sama & Etani, who in turn were distributing Concise's products through their partnership headquartered in Groton, Mass. In Japan, the company operated as Etani Shoji Kaisha, Ltd. It closed by 1992. Concise began operating under the name Concise International Co., Ltd., in 1966 and remains in business as of 2012. For other slide rules by Concise, see 1996.0141.01, 2003.0012.01, and 2006.0173.01.
References: "Concise Corporate History," http://www.concise.co.jp/eng0731/history.html; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 153–154; "Groton Engineer, Associate Design Pocket Size Rule," Groton Town Diary 13 (March 1967): 17, http://books.gpl.org/greenstone/collect/towndiar/index/assoc/D5248.dir/Vol13_1967_017.pdf.
Location
Currently not on view
date made
after 1966
maker
Concise
ID Number
1985.0636.02
accession number
1985.0636
catalog number
1985.0636.02

Concise 600 Science Tables and Circular Slide Rule

This white plastic circular slide rule is on a rectangular base that has a 4-inch ruler on the left side and a 10-cm ruler on the right. A black plastic tape attached along the top edge reads: MATLACK.
Description
This white plastic circular slide rule is on a rectangular base that has a 4-inch ruler on the left side and a 10-cm ruler on the right. A black plastic tape attached along the top edge reads: MATLACK. The top of the base is marked: CONCISE (/) SCIENCE TABLES (/) AND CIRCULAR SLIDE RULE. The slide rule has a D scale along the outer rim. A rotating disc fastened with a metal grommet has C, CI, L, A, S, T, and K scales. There is a clear plastic rotating indicator, which is labeled in red with the letters for the scales. The bottom of the base is marked: BY SAMA & ETANI.
The back of the instrument has a chart for converting temperatures from Celsius to Fahrenheit and a periodic table of the chemical elements. The bottom right corner of the back is marked: © 1968 CONCISE INTERNATIONAL CO. LTD. The left edge is marked: DESIGNED BY SAMA & ETANI, INC., GROTON, MASSACHUSETTS 01450, U.S.A. (/) MADE IN JAPAN BY CONCISE MODEL 600.
A rectangular plastic card fits inside a slot in the base. The card provides various conversion tables for energy, power, the Greek alphabet, velocity, volume, mass, force, length, and area. This side of the card is printed so that the card can be pushed out halfway from either side of the base, and the printed tables will appear right-side-up. The back of the card has tables for gas constant values and pressure, along with lists of mathematical formulas and chemical and physical data. One edge of the card is marked: ©1968 CONCISE INTERNATIONAL CO., LTD. INSERT - ST.
The instrument fits in a rectangular black plastic case. There is no instruction manual, but the instrument likely was originally accompanied by a copy of: Sama & Etani, Reference Tables and Circular Slide Rule (Groton, Mass., 1969), http://sliderulemuseum.com/Manuals/M219_refC36_Concise_SamaEtani_ReferenceTables.pdf.
The donor, Glenn Matlack, purchased this slide rule in the fall of 1968 for his junior high school general science course at Tower Hill School in Wilmington, Del. Sama & Etani designed and distributed several slide rules made by Concise. For other slide rules by Concise and the company history, see 1985.0636.02, 1996.0141.01, and 2003.0012.01.
Reference: Accession file.
Location
Currently not on view
date made
1968
maker
Concise
ID Number
2006.0173.01
accession number
2006.0173
catalog number
2006.0173.01

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