Although the key-driven calculator is generally not so well known, it is, as stated, the oldest of the modern accounting machines, and its usefulness places it in the accounting room, where it is oft-times found employed by the hundreds in figuring up the day’s work of accounting. [Sidenote: _Validity and priority of invention_] The purpose of this book is based wholly upon showing the validity and priority of invention which constitute true contributions to the Art of these two types of modern accounting machines; to place the facts for once and all time before the public in such a way that they may judge for themselves to whom the honor is due and thus settle the controversy that exists. The quibbling of court contests over the terminology of claims of patents owned by the various inventors have been set aside and only the true contributions to the Art which pertain to the fundamental principles that have made the modern machines possible, are here dealt with. The dates of patents on inoperative or impractical machines have from time to time been held up to the public as instances of priority of invention; but when the validity of these patents, as furnishing any real contributions to the Art, is questioned, they are not found to hold the theme or principle that made the modern machines possible, and as inventions, fade into obscurity. [Illustration: _Figure 1_] [Illustration: _Figure 2_ One of the Pascal Machines] The Art of either the calculating machine or the adding-recording machine is not new; it is, as a matter of fact, very old. As before stated, the Art of “accounting machine” dates back to the tenth century, but the first authentic evidence of a working machine is extant in models made by Pascal in 1642 (see illustration). THE PASCAL MACHINE Referring to the illustration, Fig. 1, of Pascal’s machine on the opposite page, it will be noted that there are a series of square openings in the top of the casing; under these openings are drums, each numbered on its cylindrical surface. [Sidenote: _Description of Pascal’s invention_] As the machine illustrated was made to figure English currency, the two right-hand wheels are numbered for pence and shillings, while the six wheels to the left are numbered from 1 to 9 and 0 for pounds. [Illustration: Blaise Pascal] The pounds register-drums, or numeral wheels, are each operated by a train of gearing connecting them with a ten-armed turnstile wheel which form the hub and spokes of what appears to be a series of wheels on the top of the casing. While the spokes and hub are movable, the rims of these wheels are stationary and are numbered from 1 to 9 and 0. The geared relation between the turnstile wheels and the numeral wheels is such that rotating a turnstile will give like rotation to its numeral wheel.