Everybody hates a prodigy, detests an old head on young shoulders.

*Desiderius Erasmus*

The German engineer Christel Hamann (1870-1948) is an outstanding figure in the world of mechanical calculators. He is a holder of numerous patents (in the USA, Canada, Germany, Sweden, Switzerland, and Great Britain) in this area and the constructor of countless mechanisms and calculators, let’s mention only Gauss, Berolina, Mercedes Euklid, Hamann Manus, Trick, Tasma, a differential engine, etc. Let’s examine two of Hamann’s remarkable calculating machines.

**Gauss Calculator of Christel Hamann**

The idea of Gauss Calculator, based on the stepped drum of Leibniz, mounted in the center of the machine, was not a new one. As early as the middle 1860s the brilliant Swedish engineer Axel Jacob Petersson invented a very interesting machine of this type, but it didn’t become popular, and only several devices had been produced.

At the end of 1899 a local Berlin businessman (merchant), Paul Haack (it is unknown if Haack was aware of the machine of Petersson, but let’s mention only an interesting detail—the family name of Petersson’s wife was Haak, maybe just a coincidence?!) contacted Hamann, with the idea to create a practical and handy calculator, as opposed to the heavy mechanical calculators of the day. Hamann welcomed this idea, as the *Landwirtschaftliche Hochschule Berlin *had already contacted him with such a request (to construct a small calculator to be used by surveyors), thus Haack and Hamann signed an agreement.

It is not clear what exactly was the role of Haack in future cooperation, but the first patents for the device have been granted namely to Haack, as an inventor or as an assignor of Hamann. Most probably Haack provided the financial support, while Hamann was in charge of the construction. At some point, however, the cooperation between Haack and Hamann abruptly ended and during the next years both of them tried to patent the ideas of the machine and they applied for and had been granted quite a few patents in different countries. Finally, both Hamann and Haack received in 1902 patents for some kind of device (see their first US patent US703785), but only Hamann managed to launch it on the market.

Only several months at the end of 1899 had been enough for the genius Hamann to prepare the first model of the machine, and it was exhibited at the Paris Exposition Universelle of 1900, where it was awarded a gold medal. Industrial production of an improved model was commenced in 1905, and the sales were handled by the mail-order house R. Reiß in Liebenwerda in Saxony.

The machine was in production 1905-1911 in Mathematisch-mechanisches Institut Hamann and in Mercedes-Bureau-Maschinen-Gesellschaft in Berlin (in 1907 Hamann’s company was bought by Mercedes Bureaumaschinenwerke). Some 1000 devices have been produced. Dimensions of the first model are: diameter 12.5, height 10 cm; weight 2.6 kg with base, 850 g without the base. In 1906 was presented a new model, the so-called Mercedes Gauss (see the nearby image), with almost the same construction, but was slightly bigger.

**The Differential Engine of Christel Hamann**

In 1905 The Royal Prussian Academy of Sciences in Berlin placed a considerable sum (15000 Marks, later on Imperial Academy of Sciences in Vienna granted additional 8000 Krones) at the disposal of German professors Julius Bauschinger (Director of the Imperial Observatory of Strasbourg) and Johann Peters (assistant of the Royal Astronomical Calculating Institute of Berlin), in order to prepare and publish tables of logarithms to eight digital places of all numbers from 1 to 200000.

The work started using hand calculations in 1908, but the progress was so slow, that in the same year Bauschinger and Peters contacted Christel Hamann and asked him to put his long experience at his disposal and to construct a new machine, by means of which the values were to be reckoned from the second differences by summation and at once written down.

Hamann readily accepted the challenge. Only several months were enough for the genius-constructor, and the machine (see the nearby photo) was ready at the beginning of 1909. It immediately went into action, worked perfectly, and surpassed all expectations.

The machine (without a printing unit) was 145 cm wide, 20 cm high and about 44 cm deep. Weight was 40 kilograms.

The machine consists of three parts: two similar independent calculating machines (adders), and a printing unit. Each of the two machines consists in turn of a switch and a counter. In the first adder placed next to the user, the second difference is added to the first difference. With the second added in the middle part, this sum is added to the intermediate result, while the third section, the printer, prints the result onto a strip of paper. All differences and the result can be set, operated, and printed with sixteen places. Each of the two adders is driven by its own handle.

The book Tables of Bauschinger and Peters (Logarithmic-Trigonometrical Tables with eight decimal places from 1 to 20000) was published in Leipzig in 1910. A description of the machine of Hamann can be found in the preface of the book, click here to see it. (digitalized in PDF format by Stephan Weiss, www.mechrech.info).

#### Biography of Christel Hamann

Christian (sobriquet Christel) Bernhard Julius Hamann was born on 27 February 1870, in Hammelwarden, a village between Oldenburg and Bremerhaven in Niedersachsen, Germany. He was the son of Georg Wilhelm Christian Hamann (born 1834 in Oldenburg, son of Hans Joachim Hamann, a musician in Eutin, and Anna Catherina Stuck), a border guard and later usher in Ellwürden, and Catherina Margaretha Louise (b. 1837 in Oberhammelwarden, daughter of the fisherman Christian Schumacher).

It seems Christel Hamann owes his interest in the mechanics and construction of calculating machines to one of his father’s friends, namely the Würzburg Professor of mathematics Dr. Eduard Selling. In the 1880s Selling devised a calculating machine of very original construction (see the machine of Selling), and the young Christel was allowed to take part in the building of this peculiar calculating machine. This collaboration with Prof. Selling must be regarded as crucial for the later life of Hamann.

Obviously from his youth Hamann demonstrated an extreme talent and energy in technics. As a teenager he attended a local technical school in Bremerhaven, working at the same time as an apprentice-mechanic at the *Nautischen Institut bei W. Rudolph* in Bremerhaven. Then he worked in *Mathematisch-Mechanischen Institut von A. Ott* in Kempten (Allgäu), in workshops of Carl Zeiss in Jena and in the workshop of Carl Bamberg in Berlin. In 1896 Hamann became independent by starting his own institute in Berlin—the Mathematical-Mechanical Institute in Berlin-Friedenau.

Initially, he dealt with the construction of geodetic and mathematical instruments (his first patent DE88223 is from 1895 for *planimeter*), which he developed after new scientific ideas and also successfully introduced into practice and for which at the 1900 World Exhibition in Paris he was awarded the gold medal. Later Hamann devoted a part of his time to construction of textile machinery, cinematographic, medical, and anthropological tools, and miniature steam engines. At the beginning of the 1900s Hamann however recognized the disadvantages of fragmentation of his interests and decided to concentrate on the construction of calculating machines.

Hamann started to develop his first calculating machines in 1898. Initially, he had the intention of using the construction of Selling, which he knew perfectly, and the resulting construction was simple, but not reliable enough. Then he decided to use the stepped drum of Leibniz, developing two very good calculating machines—”Gauss” and “Berolina”. In 1903 he designed the so-called *proportional system of levers* (parallel racks that are proportionally displaced by a lever connected to the racks), which was later used in the famous calculator “Mercedes Euklid”.

In 1909 Hamann constructed a perfect differential engine, used in the calculation of Logarithmic-Trigonometrical Tables of Bauschinger and Peters.

After WWI Hamann worked for the company *Berliner Deutschen Telephonwerke- und Kabelindustrie AG* in Berlin as chief engineer, but it seems that he essentially ran a daughter company *Hamann Rechenmaschinen*. In 1922 he developed a new type of calculating mechanism, the so-called *Schaltklinke *(switching-latch-wheel), which for the first time allowed an automatic division. The first calculating machine equipped with this mechanism was the four-species calculator “Hamann Manus” from 1925.

Further improvements of Hamann were electric drive models, “Hamann, automatic Z, Y and X”. The “Hamann Automat V” worked the first time with an automatically truncated multiplication. The “Hamann Selecta” was equipped with two full keypads, the new multiplication has already allowed during the operation of the machine. Hamann’s other inventions include the improved computing machines “Hamann Selecta”, “Hamann Elma” and “Hamann Delta”, as “Hamann Selecta” has two full keyboards, allowing new multiplications to be performed during ongoing work steps of the machine.

In 1933 Hamann was appointed as an honorary doctor of the *Technische Hochschule Berlin* (now Technical University of Berlin).

Hamann was married to Hedwig Schindler (1872-1949), but the pair didn’t have children. Christel Hamann died on 9 June 1948, in Berlin.