We are all familiar with the typewriter and the legible printing it produces. But suppose instead of printing each letter separately the whole word should be printed at once by a single-key depression, then, of course, single-letter words, such as the article “a” or the pronoun “I” would also have to be printed by a single-key depression. In this supposition we find a parallel of the requirements of a recording-adding machine. [Illustration] [Illustration: Drawings of Ludlum Patent No. 384,373] [Sidenote: _Inoperative features of early recording mechanism_] If it were possible to so increase the leverage of the typewriter keys enough to cause a word of ten letters to be printed as legibly as a single letter is now printed, ten times the power would have to be delivered at the type-head. Then think what would happen with that same amount of power applied to print the letter “a,” or letter “I.” You would not question that under such conditions the type would break a hole in the paper. And yet the patentees of the said described inventions wanted the public to believe that their inventions were operative. But to be operative as recording-adding machines, they must meet such variable conditions as described. It is useless to believe that a variation of from one to ten or more type could be printed by a set amount of pressure through an ink-ribbon and be legible under all circumstances. While the needle-type of Pottin may have printed the items legibly enough for a cash register, it would not serve the purpose of a record for universal use. The use of regular type and the inking ribbon proposed in his specification would bring it within the inoperative features named. THE LUDLUM MACHINE In 1888, about two months prior to the issue of the Burroughs recording machine patent just referred to, a patent was issued to A. C. Ludlum for an adding and writing-machine. (See illustration on opposite page.) [Sidenote: _Adding mechanism attached to typewriter_] It will be noted by reference to the drawings that the scheme is that of a typewriter with an adding mechanism attached. The details of the typewriter may be omitted, as most of us are familiar with typewriters. A feature that differed from the regular typewriter, however, was that the machine printed figures only and the carriage operated in the opposite direction, thus printing from right to left instead of left to right. [Sidenote: _Description of Ludlum machine_] A series of numeral wheels and their devices for the transfer of the tens, designed to register the totals, are shown mounted in a shiftable frame connected with the bar marked F, with the typewriter carriage, and is claimed to move therewith.