The difficult is what takes a little time. The impossible is what takes a little longer.
On 2 February 1864, Emile Grandjean, a French watchmaker (horlogère) from Fumay (Ardennes), received a 15-year patent (see French patent N°61637) for an adding machine, called Additionneur Grandjean. The Scottish pastor Brown’s Rotula Arithmetica from the 1690s can be seen as the archetype of all of these concentric toothed-disk-adding devices. Besides the patent application, nothing is known about Additionneur Grandjean, so most probably it remained only on paper, but its principle was implemented several decades later in quite a few simple adding devices like French l’Infaillible, German Revisor, Union, Optima, Maxima, Duplo, and Triplo by Jewrem Ugritschitsch and Dr. Albert Hauff from Berlin, English Adal, and others. Let’s examine one of the Grandjean-like devices—the Adal Calculator.
The spiral mechanical calculator, called Adal Calculator, was produced in the early 20th century (1907-1915) by Adal Company, Temple Courts, Birmingham (ADAL is formed from the first letters of the names of the company owners—Armand Dreyfus and Alfred Levy, German Jews, who lived in England). It is a single-row adding machine with a diameter of 197 mm, 5 mm thick, 117 gr. weight, which consists of a pair of metal disks and a cursor. The base is a flat aluminum disk with the numbers 00 to 99 around an outer ring which forms a lip. Concentric with this disk, and laid upon it, is a thin brass disk which has one hundred small semi-circular indents and the numbers 00 to 99 in a ring around it. The main part of the upper disk is formed into a spiral of 11 turns. There is a tongue of brass attached to the central bolt, that has a slot in which a steel ball slides as it accumulates turns of the spiral disk. The slot of the tongue has the numbers 1 to 11 marked on it at intervals equivalent to the step between adjacent turns of the spiral. At its further end is a small clamp that holds it at the zero point of the outer ring so that it acts as a stop for the rotation of the accumulating spiral disk.
The whole calculator is held in the flat of the hand. It is a simple adder to 1199 with addends 1-99. The spiral disk is turned by a stylus set into the indent of the number to be added until it reaches the stop. As each number is added the spiral disk rotates and the small steel ball slides in the slot in the tongue indicating the hundreds count of the accumulated result. The total result is thus the number indicated on the tongue (being the hundreds digit) plus the number indicated in the end gap of the stop.
The Adal Calculator was patented in Great Britain (patents GB190705779 and GB190900621), the USA, and Canada (see the first US patent). It seems Dreyfus and Levy bought the rights for the design from Ugritschitsch and were allowed to serve the English and American markets. In 1909, the Addall Co. was incorporated in New York to manufacture the calculating machine.