17th cen pocket calculator to fetch 100k pounds at UK auction

An 'exceptionally rare' pocket-sized French calculator from the 17th century is expected to fetch up to a whopping 100,000 pounds at an auction here.
The Arithmetical machine, measuring 14.5 cm in width and 32.5 cm in length, is one of the earliest mechanical calculating devices known to exist and is the first portable device; only three other known examples of this design have survived.
The French instrument crafted by Parisian mechanician and watchmaker Rene Grillet de Roven dates back to 1673.
It will be offered in an auction at Christie's, South Kensington, on October 10, where the piece is expected to fetch between 70,000 pounds to 100,000 pounds.

"This pocket-sized calculator is one of the earliest surviving pieces in the history of the computer," said James Hyslop, head of Travel, Science and Natural History at the auction house.
"Mechanical calculators date from the 1640s, but were big clunky brass machines. This small lightweight machine, based on Napier's logarithm was one of the earliest portable designs," he said in a statement.

The calculating device, contained in a walnut wooden box, comprises 24 rotating dials arranged in three rows of eight located on the interior lid.
Each wheel consists of several concentric circles, while the bottom of the box contains a set of rolling cylinders carrying logarithmic tables.

Grillet exhibited his pocket-sized machine during the 1670s and 1680's at markets and fairs throughout Paris and the Netherlands.
The machine performs all the arithmetic operations including addition, subtraction, multiplication and division through the use of these rolling rotating Napier's bones.
Napier's bones is a clever multiplication tool invented in 1617 by mathematician John Napier of Scotland.
The bones are a set of vertical rectangular rods, each one divided in 10 squares. The top square contains a digit and the remaining squares contain the first 9 multiples of the digit. Each multiple has its digits separated by a diagonal line.

When a number is constructed by arranging side by side the rods with the corresponding digits on the top, then its multiple can be easily obtained by reading the corresponding row of multiples from left to right while adding the digits found in the parallelograms formed by the diagonal lines.