Who built the first electric/electronic adder?

Question

The first electricity-based adder presumably used relays. (The electromechanical relay was invented for the electrochemical telegraph for repeaters in 1831 by Joseph Henry (1797-1878). I can't figure out who created the first adder, however. It's also not clear to me if the first adder was binary or decimal. I think that it was probably a ring-adder in Base 10, similar to those used on the Univac, but I have no evidence, and I've been unable to find the answer for some time now.

EDIT: Hollerith's patents (395,781, 395,782 and 487,737) do not describe an adder. Indeed, the only mention of addition is in 395,782 patent, which states: "A method for compiling such statistics must be capable of counting or adding units according to single statistical items or combination of such items." So it's not clear from this if Hollerith had an existant adder, or if he had one and decided to keep it a trade secret.

The appliation also states:

So clearly Hollerith had relays and he understood about adding... but he didn't have an adder. The 395,781 patent states: "When deemed advisable, mechanical counters may be included in the circuits containing electromagnets, for indicating the number of cards deposited in the boxes." So Hollerith used mechanical counters, which date back to the invention of the Step Rockoner and Leibniz.

So who build the first electric/electronic adder?

EDIT2: Now I'm beginning to remember that they were created for the Geiger Counters, and that Mauchly saw them and realized that if you could do addition, you could do everything.

Answer 1

Well, there is no definite answer, as an electric or even electronic adder would be useless before other machinery/circuitry would be available to feed it and take results fast enough to make it worthwhile. This wasn't the case way into the 40s as up to them (electro) mechanical adders were not only sufficient well developed, but also quite capable to peep up with data feed.

Some cornerstones here might be:

• Holleriths electromechanical counter of the mid 1880s, used in early tabulators - after all, counters can be used to add.
• Electric driven mechanical calculators ca. 1900 (real adders)
• Stibitz' Model K Adder in 1937 (relay based, just the adder, no real use)
• Zuse Z1 in 1938 (mechanical computer driven by an electric motor)
• Helmut Schreyer's 'Versuchsschaltung' of 1938 were he demonstrated the ability to turn Zuse's mechanical ALU can be done with tubes.
• Zuse Z2 in 1940 (relay based CPU, mechanical memory)
• Zuse Z3 in 1941 (fully relay based computer)
• The ABC of 1942 (tube based adder)
• Helmut Schreyer's experimental computer of 1942 (tube based)

After 1945 development of computers able to use the advantage of electric/electronic adders/ALUs did take off, so pick your favourite for 'first' and make sure to select enough attributes to make it the fitting one :)