Mechanical Calculator - The 17th Century - Calculating Clocks: Unsuccessful Mechanical Calculators

Calculating Clocks: Unsuccessful Mechanical Calculators

Both Pascal and Leibniz tried to design some kind of calculating clock before inventing their machines.

...I devised a third which works by springs and which has a very simple design. This is the one, as I have already stated, that I used many times, hidden in the plain sight of an infinity of persons and which is still in operating order. Nevertheless, while always improving on it, I found reasons to change its design... —Pascal, Advertisement Necessary to those who have curiosity to see the Arithmetic Machine, and to operate it, (1645) When, several years ago, I saw for the first time an instrument which, when carried, automatically records the numbers of steps by a pedestrian, it occurred to me at once that the entire arithmetic could be subjected to a similar kind of machinery so that not only counting but also addition and subtraction, multiplication and division could be accomplished by a suitably arranged machine easily, promptly, and with sure results —Leibniz, on his calculating machine, (1685)

The principle of a calculating clock (input wheels and display wheels added to a clock like mechanism) for a direct entry calculating machine couldn't be implemented with the technological levels of the 17th century because their heavier and more numerous gears could be damaged when a carry had to be moved several places along the accumulator. The only 17th century calculating clocks that have survived to this day do not have a machine wide carry mechanism and therefore cannot be called mechanical calculators. The first true calculating clock was built by the Italian Giovanni Poleni in the 18th century and was a two-motion calculating clock (the numbers are inscribed first and then they are processed).

• In 1623, Wilhelm Schickard, a German professor of Hebrew and Astronomy, designed a calculating clock which he drew on two letters that he wrote to Johannes Kepler. The first machine to be built by a professional was destroyed during its construction and Schickard abandoned his project in 1624. These drawings had appeared in various publications over the centuries, starting in 1718 with a book of Kepler's letters by Michael Hansch, but in 1957 it was presented for the first time as a long lost mechanical calculator by Dr. Franz Hammer. The building of the first replica in the 1960s showed that Schickard's machine had an unfinished design and therefore wheels and springs were added to make it work. The use of these replicas showed that the single tooth wheel, when used within a calculating clock, was an inadequate carry mechanism. (see Pascal versus Schickard).

• Around 1643, a French clockmaker from Rouen, after hearing of Pascal's work, built a calculating clock of his own design. Pascal fired all his employees and stopped developing his calculator as soon as he heard of the news. It is only after being assured that his invention would be protected by a royal privilege that he restarted his activity. A careful examination of this calculating clock showed that it didn't work properly and Pascal called it an avorton (aborted fetus).

• In 1659, the Italian Tito Livio Burattini built a machine with nine independent wheels, each one of these wheels was paired with a smaller carry wheel. At the end of an operation the user had to either manually add each carry to the next digit or mentally add these numbers to create the final result.

• In 1666, Samuel Morland invented a machine designed to add sums of money, but it was not a true adding machine since the carry was added to a small carry wheel situated above each digit and not directly to the next digit. It was very similar to Burattini's machine. Morland created also a multiplying machines with interchangeable disks based on Napier's bones.

• In 1673, the French clockmaker René Grillet described in Curiositez mathématiques de l'invention du Sr Grillet, horlogeur à Paris a calculating machine that would be more compact than Pascal's calculator and reversible for subtraction. The only two Grillet machines known have no carry mechanism, displaying three lines of nine independent dials they also have nine rotating napier's rod for multiplication and division. Contrary to Grillet's claim, it was not a mechanical calculator after all.