In early 1890s, the German civil engineer Heinrich Esser (1845–1906), who lived in Aachen, where he worked as municipal police building inspector, invented as a hobby and in his spare time a mechanical calculating machine, which he later patented in Germany (patent №82965, 10 December 1892), and USA (patent No. 561099, 2 June 1896) (he took a vacation in June 1892 to register his invention at the imperial patent office in Berlin).
The Esser calculating machine is a four-species device, i.e. it is capable of adding, subtracting, multiplying and dividing. Only one example of the machine survived to the present, and it is kept in the collection of Arithmeum museum in Bonn, Germany (see the nearby image).
Interestingly, the comparison of the patent and the exhibited in Arithmeum machine shows that the latter is an older prototype, as several essential details of the patented machine are missing. The Esser machine in the Arithmeum does not have tens-carry in the revolution counter, which is necessary in order to be able to do abridged multiplication and division. There are also other missing features which mark this machine out as an early model: the main crank has no rest position lock, and there is no bell to signal an overflow of the result mechanism. The inventor must also have envisaged the mass-production of his machine, as it consists of modules that can easily be exchanged (which was absolutely unusual at the time), to meet the individual needs of customers with respect to capacity. Let’s examine the Esser calculating machine, using the patent drawing (see the image below).
The Esser calculating machine comprises three indicators, which may be designated as “operating-indicator” (marked with A on the drawing), “product-indicator” (marked with C), and “quotient-indicator” (marked with B), because by setting a number as multiplier in the quotient-indicator and a number as multiplicand in the operating-indicator the product-indicator, after manipulating with the operating-indicator in one direction, shows or indicates the product of the multiplication, and, vice versa, by setting a number on the product-indicator as the dividend and a number in the operating-indicator as the divisor and manipulating the operating-indicator in a reverse direction the quotient-indicator will show or indicate the result of the division.
The main advantage of Esser calculating machine over the other calculating machines of the time was during the multiplication, when an abridged method may be employed by which considerable time and labor are saved. If a large number (say 33333) is to multiplied, for instance, with the number 2479, the operation may be performed on this machine in the same manner as is employed on the other machines—i.e., the multiplication of two factors may be carried on in the usual way, in which the main shaft is to be turned 9+7+4+2=22 times (according to the digits of the multiplier). However, the Esser machine allows an abridged method to be employed, in which the main shaft is to be turned only 10 times. What a great improvement!
Biography of Heinrich Esser
Little is known about Heinrich Esser. He was born in Pingsheim in the Euskirchen district in 1845. After graduating from high school in Düren, Esser studied civil engineering in Berlin and at the Technische Hochschule Aachen, where he passed the construction manager examination in 1874. He was a government builder at the Royal Railway Directorate in Cologne and later a municipal police building inspector in Aachen, where he died in 1906.