Slide rules and other calculation instruments

Slide rules and other calculation instruments

Curated by Evelyn Sander, George Mason University

Please come visit this exhibit on display at George Mason University in the math department display case in the atrium on the first floor of Exploratory Hall.

For centuries, the slide rule was the leading device used for multiplication, division, and other operations (though adding machines were separate devices). The use of these devices ended  in 1972 when Hewlett-Packard calculators became the one-in-one go to device for all four basic arithmetic operations. 

This exhibit includes slide rules and other non-electronic calculating devices that would have been an integral part of the daily life of any scientist, mathematician, or engineer prior to 1972. 

Timeline

• 1614 John Napier discovers the logarithm function
• 1620s Invention of the slide rule, credited to Edmund Gunter, Edmund Wingate, William Oughtred 
• 1845 Invention of specialized nautical slide rule
• 1930s Invention of specialized aviation slide rule, still sometimes used as a backup device
• 1969 Astronauts in moon landing brought slide rules for last minute calculations
• 1972 Hewlett-Packard calculator makes slide rules obsolete

How slide rules work

The logarithm function has a powerful property: it converts multiplication into addition and division into subtraction.

The slide rule is a clever set of two logarithm tables such that by carefully matching up the numbers, multiplication reduces to an addition problem. Specialty slide rules include other number tables, such as  trigonometry, fuel efficiency, or prices.

Items in our collection

Russian abacus

On loan from Mary Nelson

The abacus has been used for millennia, and unlike the rest of Europe and the United States, Russians continued to abaci for basic arithmetic, until Soviet production of electronic calculators in 1974. 

Circular slide rule

On loan from Thomas Wanner

A circular slide rule is smaller than a linear slide rule, thus fitting better in a pocket. 

Slide rule and belt holster

On loan from David Walnut

This slide rule fits into  a leather holster, worn on the belt. 

Cylindrical slide rule

Donated to the GMU Department of Mathematical Sciences

Keuffel & Esser Model 1741 Thacher Cylindrical Slide Rule

This premier instrument’s cylindrical design makes it possible to get accuracy equivalent to a 59 foot conventional linear slide rule.  The US patent is dated 1881. Device sold from 1883 from1950. (Its box is also depicted below.) 

Linear pocket slide rule

On loan from Karen Crossin

This is a classic slide rule of the type that an engineering student would be expected to carry. It was used by Howard Wheatley. 

Retail store slide rule

On loan from Donald Nadeau

A specialty slide rule from the 1930s,  used for calculating retail markups and other 

calculations for operating a retail business.  

Adding Machine

On loan from Melissa Talbot

An adding machine was used whenever adding rather than multiplication was required. This includes anything from sales to data collection. This Clary adding machine (circa 1950) was used by Larry Burslie to do taxes for the people of Fertile, MN until the mid-1970s.

Gaps in our collection

(which we would love to fill)

Astronaut Buzz Aldrin brought this slide rule to the moon for last minute calculations. Purchased by a  serious collector in 2007 for $77,675.00.

Astronaut Buzz Aldrin

Aviation slide rule

World War II Load Adjuster slide rule

For further reading see: 

http://www.npr.org/sections/ed/2014/10/22/356937347/the-slide-rule-a-computing-device-that-put-a-man-on-the-moon (NPR article on the history of slide rules and their current classroom uses)

http://www.oughtred.org (organization of slide rule collectors)

http://sliderulemuseum.com (images of slide rules from outside the collection come from this site) 

http://americanhistory.si.edu/collections/search/object/nmah_1131290 (this gives more information about the cylindrical slide rule)