Christian Ludwig Gersten

Smallness of mind is the cause of stubbornness, and we do not credit readily what is beyond our view.
Francois de la Rochefoucauld

The prototype of Gersten's machine kept in Darmstadt until 1943
The prototype of Gersten’s machine kept in Darmstadt until 1943

In 1735 Christian Ludwig Gersten (1701-1762), a professor of mathematics at the University of Gießen, traveled to London, to be elected a fellow of the Royal Society and to present to the Society his project of an arithmetical machine. In his description, he claims, that the machine had been designed 12 or 13 years before, most probably in 1722.

The machine was described in the scientific journal Philosophical Transactions of the Royal Society Nr. 438 for the months of July, August, and September 1735 (pages 79–97). In his 19-page detailed presentation, named Description and Use of an Arithmetical Machine… (see description of the machine of Gersten) Gersten mentioned, that he has been acquainted with the machines of Morland, Leibniz, Poleni, and Leupold, and learned that Charles Pascal invented one, and was inspired from them (especially from Leibniz) to create his own calculating device.

A sketch of Gersten's machine from the presentation to the Royal Society
A sketch of Gersten’s machine from the presentation to the Royal Society

The first prototype of the machine was wooden, and after the device had been shewed to some Patrons and Friends of Gersten, they encouraged him to continue the development. The second copy was made from brass and at the end of 1725, Gersten presented it to the Landgrave of Hessen Darmstadt Ludwig V and his son, Prince Georg II (who became Landgrave in 1726). The Landgrave admired the inventor and encouraged him to try to popularize it. Besides the presentation to the English Royal Society, the description of the machine was sent and approved by the French Academie Royale des Sciences, and in 1735 the description was published in the first book of six volume set of Jean Gaffin Gallon—Machines et inventions approuvées par l’Academie Royale des Sciences, depuis son établissment jusqu’a présent; avec leur description.

In 1736 a copy (probably the only prototype) of the machine of Gersten was donated to the Landgrave of Hesse-Darmstadt and was kept in the Castle of Darmstadt until WWII (see the first figure), when it was destroyed by bombs in 1943.  Fortunately, to the present day managed to survive a replica of the device from 1920, made by order of Dr. Franz Trinks, the founder of Rechenmaschinenfabrikation in Braunschweig which is preserved in the Braunschweigisches Landesmuseum (see the third figure).

Let’s examine the arrangement of the machine in the sketch from the presentation to the Royal Society (see the sketch in the second figure).

A copy of Gersten's machine in Braunschweigisches Landesmuseum
A copy of Gersten’s machine in Braunschweigisches Landesmuseum

The dimensions of the machine are—36 cm in width, 37 cm in height, and 7 cm in thickness. It has a six positional input mechanism and seven positional display mechanism (from the design of the machine is evident, that it can be easily extended with additional positional modules). In part 1 of the upper figure are shown the first three digital positions—for units (marked with AA), for tens (marked with BB), and for hundreds (CC). Every position has two sliders, the first of them (the upper one) Gersten named operator, the second one—determinator. The determinator indicates what number will be entered in the calculating mechanism, while the entering is done by moving the operator.

The main element in the calculating mechanism of the machine are ratchet-wheels. They are used in the digital dials for entering numbers, and for tens carry during the calculations.

At the end of his presentation, the inventor acknowledged, that the major constructive problem of the machine is significant friction between the parts of the mechanism when must be done tens carry for two or more digital positions.

The machine of Gersten is not as elaborate and easy to operate, as the machines of the other early inventors, but nevertheless, it is well-designed and fully capable of calculations device. Interestingly, there is a letter
from Johann Müller from 9 February 1784 to his friend Lichtenberg in Göttingen, in which he writes the following about Gersten: “Unexpectedly, I found the calculating machine of the former local Prof. Gersten in the castle in Darmstadt, of which I hereby provide you with a description and drawing. Maybe you can make some use of it. It is strange that the thought of whether not appropriated in perfection is what I give you on my wooden models to be the more comfortable and faster installation of the given digits.”

Biography of Christian Ludwig Gersten

Johänn Christian Ludwig Gersten (or Gerstein) was born on 7 February 1701, in Gießen, a town in the German federal state of Hessen. He was the son of Johann Justus Gerst(en) (1666-1712), and Maria Margaretha Uhrban (1666-1741). Johann Gerst was a lawyer, Fürstlich-Schwarzburgischer Kanzler und Konsistorial-Präsident in Sondershausen (a town in Thuringia), who married Maria Uhrban in 1692, and they had seven children: Carola Henrica Eleonore (1693-1720), Johann Christian (b. 1695), Juliana Charlotte (1698-1726), Christian Ludwig (1701-1762), Friedrich Ludwig (1703-1705), Christine Frederike (b. 1706), and Johann Maria Lucia.

From 1718 Gersten studied law and mathematics at the University of Gießen and at the beginning of the 1730s he traveled to London, England, to improve his mathematical knowledge. In London, in 1733 he became a fellow of the English Royal Society. In May 1733, he returned back to Gießen, to accept the position of a professor of mathematics at the University of his hometown, which he held until 29 Apr 1745.

As a scientist, Gersten is primarily known for his dissertation work, published later as a book, describing a series of experiments, using the barometer, titled “Tentamina Systematis Novi ad Mutationes Barometri ex Natura elateris Aerei demonstrandas, cui adjecta sub finem Dissertatio Roris decidui errorem Antiquum et vulgarem per Observationes et Experimenta Nova excutiens” (see the nearby image). Gersten as a matter of fact was the first scientist to find out, based on observations, that dew did not fall from the heavens, but ascended from the earth, especially from plants. He is also the author of several other books in the fields of astronomy, physics, and mathematics.

As we already mentioned, in 1735 Gersten traveled again to London, to present to the Royal Society his project of an arithmetical machine.

It seems Gersten was quite an active person not only in the field of science but also in public affairs, which later led him into severe troubles. Gersten was admired in 1725 for his calculating machine by Landgrave of Hesse-Darmstadt Ludwig V, and by his son, Prince Georg II, who became Landgrave in 1726. In the early 1740s, Gersten was deposed from his office after refusing to submit to the sentence of a court of law, in a lawsuit with his brother-in-law Johann Friedrich Wahl (1693–1755), a Professor and from 1735 Rektor der Universität Gießen, and in 1744 he wrote a petition to the Landgrave Georg II, which was considered as offensive. The Landgrave accused Gersten and initiated a trial against him. Having a presentiment what will be the result, Gersten decided to escape justice and in July 1744 he left the town.

Castle Marxburg bey Braubach, where Gersten was imprisoned for 12 years
Castle Marxburg bey Braubach, where Gersten was imprisoned for 12 years

Initially, he settled in Altona bei Hamburg, and informed the University officials, that he was not going to return to Gießen and lost his position in April 1745. Then he departed to St. Peterburg, Russia, maybe to some other places also, but finally decided to return to Germany. And then his disrespect to the Landgrave and the attempt to escape from justice finally got him into big trouble. In September 1748 he was arrested in Frankfurt am Main by request from Darmstadt, and condemned to lifetime detention at the castle Marxburg bey Braubach (see the nearby image).

Gersten never recognized his mistakes and repeatedly addressed the court with offensive petitions. Interestingly, despite his problems with justice, in 1748 he was partly restored as a professor at the University of Gießen and was allowed during his stay in the castle to teach young people in mathematics. Gersten was eventually released as late as 1760.

Christian Ludwig Gersten died on 13 August 1762, in Frankfurt am Main.