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Bissaker's Sturdy Slide Rule

In 1654, Robert Bissaker designed and constructed the first slide rule whose slide was placed between two parts of a fixed stock.  This proved to be more durable than other slide rules previously designed, and in fact durable enough to last to the twentieth century when slide rules weren't needed anymore.  The one pictured above was actually made by Bissaker and is the oldest known slide rule.  Little is known of Bissaker other than he worked in London as a woodworker, primarily making navigation tools for seamen.  Bissaker also created a set of Napier's bones made out of wood, rather than ivory.


Slide Rule (1623)

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The Slide Rule: 
A Combined Effort

Slide Rule

Napier had come up with a way to do munltiplication and division using logarithms, but still that took some work.  The search continued to find an easier and quicker way to multiply numbers.  Edmund Gunter used Napier's logarithms to create the precursor to the first slide rule.  He created a number line with the numbers spaced out proportionate to their logarithms.  Then a product could be found by finding one of the factors on the number line, then letting that become the new start and from that point count out the next value of the second factor.  This sum is the product of the two numbers.  A few years later, William Oughtred came along and refined Gunter's idea by making two number lines that could slide along each other, reducing the work of readjusting the starting point.  In this case, the second line was placed at the value of the first factor.  The point of the second factor was marked on the line of the first, marking the sum of the two numbers.  This was then the product of the two numbers.  Oughtred is credited for invention of the first slide rule.  Revisions were continuely made but used the original ideas of Gunter and Oughtred.  A double cursor was added in 1850 by French Artillery Officer Amedee Amnnheim.  At this time, the slide rule was called an astrolabe, due to it's significance in astrology.  The slide rule held as a common tool for many mathematicians and students of math for about three hundred years, until the emergence of the calculator as we know it now.

Bio:  Gunter

Edmund Gunter (1581-1626) was schooled in London and Oxford where he graduated in 1603.  In 1615 he earned his degree in divinity and was ordained.  He held a position in the church until he died in 1626, but his main interests remained in mathematics.  In 1619, Gunter became the professor of astronomy at Gresham College in London.  The year of 1620 was a busy year for Gunter.  Here is a list of some of his accomplishments in this year:  published seven figure tables of logarithms of sine and tangent; coined the names cosine and cotangent, and the abbreviations sin and cos; and invented Gunter’s Scale, the two-foot long scale that was the forerunner to the slide rule.

Edmund Gunter's publication

William Oughtred

Bio:  Oughtred

William Oughtred (1574-1660) was also an ordained minister as well as a mathematician.  He went to school at King’s College Cambridge, receiving his B.A. in 1596 and his M.A. four years later.  Oughtred was ordained an Episcopal minister in 1603 and though he served in the church, his mathematics continued.  He was a private tutor for many and was known for his passion towards the subject of math.  His accomplishments include: creating an early form of the slide rule in 1623; inventing the circular slide rule in 1630; being the first to use x as a symbol for multiplication and :: as a symbol for proportion (1631). 

Jessica Carlson