principal papers
Fragment of Schickard’s letter sent to Kepler in September 20, 1623:

"What you have done by calculation I have just tried to do by way of mechanics. I have conceived a machine consisting of eleven complete and six incomplete sprocket wheels; it calculates instantaneously and automatically from given numbers, as it adds, subtracts, multiplies and divides. You would enjoy to see how the machine accumulates and transports spontaneously a ten or a hundred to the left and, vice-versa, how it does the opposite if it is subtracting ... "

Fragment of Schickard’s letter sent to Kepler in February 25, 1624:

“… In other opportunity I will send you a more detailed description of the design of this arithmetic machine; in summary, it works like this: aaa are the buttons of the vertical cylinders with the digits of the multiplication table, which can be displayed at will in the windows provided for the slides bbb. The dials ddd are attached to internal toothed wheels, each one having ten teeth geared in such a way that, if the wheel of the right makes ten turns, the wheel on its left makes only one turn; and if the first wheel on the right side makes one hundred turns, the third wheel on the left makes one turn, and so on.

All the wheels rotate in the same direction making it necessary the use of another wheel of the same size geared permanently to the wheel at its left, but not with the one at its right, which requires a special attention during its construction. The digits marked in each wheel are displayed in the openings ccc of the central plate.

Finally, over the base are located the buttons eee used to note in the openings fff the numbers that need to be used during the operations. This brief description would be better understood by using the real instrument.

I had placed an order with a local man, Johan Pfister, for the construction of a machine for you; but when half finished, this machine, together with some other things of mine, especially several metal plates, fell victim to a fire which broke unseen during the night, three days ago. I take the loss very hard, especially, since there is no time to produce a replacement soon.”

hardware
The Concept
A set of revolving Napier Bones was used for multiplication.  Addition was performed by turning the dials on the lower part of the machine.  These dials were connected with internal wheels, with teeth on their circumference, causing a carry as the wheel passed from 9 to 0.  Subtraction was performed by reversing the wheel.

software

keywords

see also
Victor Enaker

related subjects

Biography

Wilhelm Schickard was educated at the University of Tübingen. After receiving his first degree, B.A. in 1609 and M.A. in 1611, he continued to study theology and oriental languages at Tübingen until 1613.

In 1613 he became a Lutheran minister at towns around Tübingen. He continued this work with the church until 1619 when he was appointed professor of Hebrew at the University of Tübingen. Schickard was a universal scientist and taught biblical languages such as Aramaic as well as Hebrew at Tübingen.

In 1631 he had rather a change of subject being appointed professor of astronomy at the University of Tübingen.

His research was broad and included astronomy, mathematics and surveying. He invented many machines like one to calculate astronomical dates and one for Hebrew grammar.

He also made significant advances in mapmaking, showing how to produce maps which were far more accurate than those which were currently available.

Long before Pascal and Leibniz, Schickard invented a calculating machine in 1623 which was used by Kepler. He wrote to Kepler suggesting a mechanical means to calculate ephemerides.

Schickard corresponded with many scientists including Boulliau, Gassendi and Kepler.

Among his other skills, Schickard was renowned as an engraver both in wood and in copperplate. Schickard died of the plague either on the day given or, possibly, one day earlier.

Chronology

Honors and awards