Overview: William Pratt (c. 1560-1620) was a prominent British mathematician and inventor best known for creating one of the world‘s first pocket calculators in 1616. Called the "Arithmetical Jewell", this portable mechanical device could efficiently perform all basic arithmetic operations as well as complex calculations – a pioneering achievement in 17th century Europe. Let‘s dive into Pratt‘s life story and examine how he devised this tool that presaged modern calculating aids we rely on today.
Path to Becoming a Math Whiz
William Pratt was born in the 1560s, likely in London or its vicinity. Historical records don‘t reveal much about his family or origins. But we know as a youngster, Pratt demonstrated exceptional mathematical abilities. He quickly mastered existing calculation techniques like the abacus, algorism, and jetons.
Eager to pursue formal studies, Pratt attended Oxford University in the 1580s – a vibrant hub for science and philosophy. Here, influenced by professor John Dee‘s research in astronomy and navigation, Pratt began honing his skills in arithmetic, algebra, geometry and trigonometry.
Thriving in London‘s Scientific Renaissance
After graduating Oxford in the 1590s, Pratt settled in London just as Elizabethan England was nurturing its first scientific Renaissance. The city buzzed with scholars challenging ancient theories about the cosmos, debating new Atlantic exploration maps, and experimenting with optics, clocks and printing – often gathered at a trading house called Gresham College.
Pratt became a renowned mathematics instructor in London frequented by future luminaries like Robert Hooke (above)
As a respected math instructor in this milieu for over 20 years, Pratt trained prosperous merchants in commercial arithmetic and accounting. He also rubbed shoulders with Samuel Foster, Edward Wright, and Henry Briggs – intellects advancing mathematics from through innovations like logarithms, spherical trigonometry and longtiude calculation.
This vibrant community and period developments in quantifying the universe kindled Pratt‘s creativity. Witnessing colleagues wrestle with arduous manual calculations, he began devising ideas for a mechanical calculating aid.
Revolutionizing Arithmetic with Napier‘s logarithms
The final spark for Pratt‘s invention came from Scottish mathematician John Napier‘s 1614 publication detailing his revolutionary discovery of logarithms – mathematical functions allowing difficult multiplications be done via basic addition instead.
While logarithms enabled faster navigation and astronomy calculations, looking up values from Napier‘s log tables remained cumbersome. Pratt realized a compact mechanical device employing logarithms could speed up arithmetic for the common man.
So drawing on 20 years of mathematical instrumentation experience, Pratt sketched designs for a pocket-sized calculator to automate complex calculations. By 1615, backed by investor John Harper, he built the first prototype.
The Game-Changing Arithmetical Jewell
By 1616, after months of experimentation, Pratt had crafted a working product – the "Arithmetical Jewell". Just a bit larger than a pocketwatch, this brass instrument had multiple numbered dials that could be rotated with a stylus to set inputs. Intricate gears and levers then displayed the calculated result in a separate counter.
What could it calculate? Using logarithms built into the mechanism, the Jewell enabled:
- All 4 basic arithmetic functions
- Roots, powers, reciprocals
- Trigonometric ratios
- Astronomical relationships
- Financial transactions
And it achieved these quickly and reliably without relying on easy-to-miscopy log tables. The Jewell was also affordable at £3-5 compared to the £15+ for traditional calculating aids. Pratt touted his invention‘s everyday utility in his 1617 guidebook titled The Arithmetical Jewell Explained.
William Pratt‘s Arithmetical Jewell Specifications
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Size: 4 inches x 2.5 inches x 0.2 inches
Weight: 5 ounces
Materials: Brass gears, wooden casing
Capacity: 4-digit numbers
Functions: Addition, subtraction, multiplication, division, squares, cubes, roots, logarithms, trigPratt built over 75 Jewell calculators in his workshop, selling many to sea merchants, military men and landed gentry. It garnered awards as a breakthrough calculating tool for non-scientists. While several similar contemporaneous devices like Bartholomew‘s Cylinder also appeared, Pratt‘s design featuring Napier‘s logs proved extremely popular.
The Arithmetical Jewell enjoys fame as one of the earliest pocket calculators – preceding Blaise Pascal‘s famous Pascaline by almost 50 years!
Perfected Over Time
William Pratt continued improving the Arithmetical Jewell over the next years with aid from his mathematician sons. The device became widely used across England and on the Continent by the early 1800s.
Renowned abbacus author John Mellis even proclaimed Pratt‘s creation as "so ordered that the youngest capacity by a little practice may worke wonders thereby". High praise for making complex arithmetic easy and portable!
Only two original specimens of Pratt‘s remarkable invention remain displayed today in European museums. Yet the Arithmetical Jewell‘s design genius remains noteworthy as one of mankind‘s first attempts to mechanize routine, error-prone calculations. Hats off to William Pratt for laying the foundations for computing tech we can no longer live without!
