In all the preceding machines the roller is used in a _horizontal_
position; but at some unknown period of past ages, another modification
was devised, one by which the power could be applied at any distance
from the center. Instead of placing the roller as before, over the
well’s mouth, it was removed a short distance from it, and secured in a
vertical position, by which it was converted into the wheel or capstan.
One or more horizontal bars were attached to it, of a length adapted
to the power employed, whether of men or animals; and an alternating
rotary movement imparted to it, as in the common wheel or capstan,
represented in the figure. It appears that machines of this kind, and
worked by _men_ were common in Europe previous to, and at the time he
wrote. Sometimes the shaft was placed in the edge of the well, so that
the person who moved it walked round the latter, and thus occupied less
space.
[Illustration: FIG. 81.]