will be positive or forward if the wheel C gears in A, and
consequently four will be added to the figure showing at the window W. But
if the wheels CC' are moved to the right, C' will gear with A moving
backwards, with the result that four is subtracted at the window. This
motion of all the wheels C is done simultaneously by the push of a lever
which appears at the top plate of the machine, its two positions being
marked "addition" and "subtraction." The B-wheels are in fixed positions
below the plate MK. Level with this, but separate, is the plate KH with the
window. On it the figure disks are mounted.

This plate is hinged at the back at H and can be lifted up, thereby
throwing the A-wheels out of gear. When thus raised the figure disks can be
set to any figures; at the same time it can slide to and fro so that an
A-wheel can be put in gear with any C-wheel forming with it one "element."
The number of these varies with the size of the machine. Suppose there are
six B-wheels and twelve figure disks. Let these be all set to zero with the
exception of the last four to the right, these showing 1 4 3 2, and let
these be placed opposite the last B-wheels to the right. If now the buttons
belonging to the latter be set to 3 2 5 6, then on turning the B-wheels all
once round the latter figures will be added to the former, thus showing 4 6
8 8 at the windows. By aid of the axis Z, this turning of the B-wheels is
performed simultaneously by the movement of one handle. We have thus an
addition machine. If it be required to multiply a number, say 725, by any
number up to six figures, say 357, the buttons are set to the figures 725,
the windows all showing zero. The handle is then turned, 725 appears at the
windows, and successive turns add this number to the first. Hence seven
turns show the product seven times 725. Now the plate with the A-wheels is
lifted and moved one step to the right, then lowered and the handle turned
five times, thus adding fifty times 725 to the product obtained. Finally,
by moving the piate again, and turning the handle three times, the required
product is obtained. If the machine has six B-wheels and twelve disks the
product of two six-figure numbers can be obtained. Division is performed by
repeated subtraction. The lever regulating the C-wheel is set to
subtraction, producing negative steps at the disks. The dividend is set up
at the windows and the divisor at the buttons. Each turn of the handle
subtra