To the unsophisticated, such a simple thing as applying keys to the ancient type of calculating machines that have been made and used for centuries, would seem but a simple mechanical application that the ordinary mechanic could accomplish. But it was too great a problem for the many renowned inventors of the older Art to solve. Even though the use of depressable keys was common to many machines, especially the piano, they knew that the organized make-up of their machines could scarcely stand, without error, the slow action received from the crank motion or other means employed as manipulating devices. To place it within the power of an operator to operate their machines at such a speed as would obtain in the sudden striking of a key would result in chaos. [Sidenote: _Patent office a repository of ineffectual efforts_] There is no room for doubt that some of these early inventors had the wish or desire to produce such a key-driven machine and may have attempted to produce one. But as they lacked the advantage of an institution like the Patent Office in which they could leave a record of their inoperative inventions, and in view of the fact that they were dependent on producing an operating machine for credit, there is no authentic proof that they made attempts in this line. [Illustration] [Illustration: Parmelee Patent Drawings] The Early Key-Driven Art M. Le Colonel D’Ocagne, Ingénieur des Ponts et Chaussées, Professeur à l’École des Ponts et Chaussées, Répétiteur à l’École Polytechnique, in his “Le Calcul simplifie,” a historical review of calculating devices and machines, refers to the key-driven machine as having first made its appearance in the Schilt machine of 1851, but that the Art reached its truly practical form in America. In the latter part of his statement the professor is correct, but as to the first appearance of the key-driven machine the U. S. Patent Office records show that a patent was issued to D. D. Parmelee in 1850 for a key-driven adding machine (see illustration). THE PARMELEE MACHINE [Sidenote: _First attempt to use depressable keys for adding was made in America_] By referring to the illustration of the Parmelee machine reproduced from the drawings of the patent, the reader will notice that the patentee deviated from the established principle of using numeral wheels. In place of numeral wheels a long ratchet-toothed bar has been supplied, the flat faces of which are numbered progressively from the top to the bottom. [Sidenote: _Description of Parmelee machine_]