The Machine Arithmetique of Jean Lépine

In the published in 1725 number of the official publication of the French Academy of Sciences—Machines et inventions approuvées par l’Académie royale is described the calculating machine (machine arithmetique) of Jean Lépine (L'épine). Jean Lépine was a skilful french mechanician and watchmaker from the beginning of the 18th century, who lived in Paris and used to work as a mechanician for the french king. An astronomical clock, made by him about 1710, was exposed at Buckingham Palace. Jean Lépine is father of the world known watchmaker Jean-Antoine Lépine (1720-1814).

It is unknown when exactly the device was designed and if a working copy was manufactured.

The machine is a 12-digital adding device. The rightmost two dials are used for adding of sols and deniers (french monetary units at this time, 1 sol is equal to 1/20 of the livre, 1 denier is 1/12 of the sol) and are divided into 12 and 20 parts. Next ten dials are decimal.

Arithmetical machine of Jean Lépine, front view

The wheels are arranged in two rows. The tens carry from the 6th (last of the lower row) wheel to the 7th (first in the upper row) dial is performed by means of a mechanical system (marked with L in the upper figure), which consists of two small rods (marked with 1), two springs (2) and a clamp (3). On every full revolution of the 6th wheel one of the pins (which is prolonged) raises the lower clamp, and pushes the side clamp, which rotates the 7th wheel to 1/10 revolution. The two springs and the clamp sidelong are destined for fixing and supporting.

The 12 wheels in the upper part of the machine are not connected one to another and can be used for storing of the intermediate results. In the lower figure can be seen the fixing mechanism of each wheel, which consists of a spring and a clamp (marked with P1 and P2) (the fixing mechanism of the lower wheels (which are destined for the showing of the result) is manufactured in the same manner). The rotating of these wheels can be done by means of clamps M (see the upper figure), which are connected with the axes of the wheels and are rotating by means of the stylus E. Over the windows, where can be seen inscribed over the periphery of the wheels digits, are inscribed the proper units—deniers, sols, units, tents and so on to the billions.

The stylus E actually has 2 edges—short and long. The entering of numbers is done by rotating of the dials, which are divided to 12, 20, 10 and so on parts. Bellow each one of these dials is mounted another dial, which has the same number divisions. Over the periphery of the lower disks are inscribed digits, whish can be seen in the windows, situated over the disks and are used for showing of the entered number.

If in the openings of the dial is pushed the long edge of the stylus, then it will be rotated together with lower disk. If it is pushed the short edge of the stylus, then it will be rotated only the upper disk, but lower disk, showing entered number, will remain static.

The result is presented in the two rows of windows, which are places over the entering dials, where can be seen 12 smaller disks F. Transfer of the digits from the entering dials to these wheel is made by a system of clamps and springs. The tens carry is done by means of a similar system.

Over the periphery of the disks F, which are placed bellow entering dials and are showing the entered number, actually are inscribed 2 rows of digits. The first row is used during the adding, the second (its digits are complement to 10 of the first row)—during the subtraction. Only one of the rows can be seen at a particular moment, and which row can be seen is determined by the clamp S, which can be seen in the left side of the figure. Rotating this clamp, we can show one or another row, depending on if we want to add or to subtract. The resetting of the result to 0 can be done by means of clamps R, which are similar of clamps M, used for entering the numbers in the recording mechanism.

Arithmetical machine of Jean Lépine, back view