Assuming that the numeral wheel of any one of the different orders registered 0 through its sight opening and the turnstile of the same order was moved one spoke of a rotation, it would move the wheel so that the 0 would disappear and the figure 1 would appear; now if we should move the same turnstile three more spokes the numeral wheel would move likewise three spaces and the 4 would appear. A stop in the form of a finger reaching over the spokes is provided to stop the turnstile at the right point so that the figures on the numeral wheels may register properly with the sight openings in the casing. [Sidenote: _Constructional features of the Pascal machine_] The figures on the wheel rims fast to the casing are arranged anti-clockwise to register with the space between the spokes, the 0 registering with the first space, the 1 with the second space and so on around the wheel. Thus by use of the finger or a stylo inserted in a space opposite the number to be added, the operator may move the spoked wheel or turnstile clockwise until stopped by the stop finger. By repeated selection and operation for each figure to be added, the wheels will be revolved through their cycles of rotation caused by the accumulation. As the numeral wheels complete each rotation the 0 will appear, so that a registration of the tens must be made. Pascal provided for the accumulation of the tens by automatically turning the wheel of next higher order one point through the action of the lower wheel. The novel means employed for this transfer of the tens consisted of a one-step ratchet device operated by a pin in the train of gearing connected with the lower numeral wheel, which, as the lower wheel passed from 9 to 0, forced the lever to which the ratchet pawl was attached in a direction to cause the gearing of the higher numeral wheel to be ratcheted forward far enough to add one to the higher numeral wheel. The direct actuation of a numbered wheel through its various degrees of rotation and the secondary feature of effecting a one-step movement to the numbered wheel of higher order (which seems to have been originated by Pascal) is the foundation on which nearly all the calculating machines have since been constructed to calculate the combinations of the Arabian numerals represented in Addition, Multiplication, Subtraction and Division. In Fig. 2 of the illustration of Pascal’s machine, the machine has been reversed, and the bottom of the casing, which is hinged, thrown back, showing the numeral wheels and gearing of the different orders and the transfer levers for the carry of the tens. [Sidenote: _Increased capacity of modern calculator_] The Art of the modern machines is far removed from the older Art by its greatly increased capacity for rapid calculation which is found emanating from the provision of keys as the means of manipulation.