ers on diametrically opposite sides, carries the marks
of conjunction and opposition of the luminous bodies, with a movement
equal to the course of the sun from lunar apogee or perigee. The lowest
index, fitted with a single pointer, indicates the motion of the moon
from its apogee or perigee. Under these three indices, there is situated
a common circle, divided into 12 parts, each of which are further
divided into 30 parts through its outer circumference. I have said a
common circle, for, with respect to the first index, the division
represents 12 hours, and the double subdivision representing the double
set of minutes of the hours serves for an excitator for anytime at all,
at will. For as often as the little index reaches the twelfth hour,
first being moved by hand wherever you prefer, a little hammer strikes
the little bell many times. But if you observe the second or the third
index, the first division provides the signs, and the subdivision of the
signs gives the individual degrees of the distance of the sun from the
lunar apogee, or of the moon from its apogee, respectively. To this is
added two other interior circles from the same center: to the larger is
inserted the equation of the center of the moon in its conjunctions and
oppositions; and on the smaller the equation of the same moon in its
quarters, astronomically-geometrically proportioned to the distance of
the moon from its apogee or perigee. In the first case, the equation is
to be subtracted from the mean longitude of the moon, descending from
apogee to perigee; in the second case, to be added to the mean longitude
of the moon ascending from perigee to apogee; and, in the third
semicircle of the index, as the rubric directs, common to both
equations, added around the center.

V

Perpendicularly under the center of the machine, two other indices are
carried about one and the same center. The one nearer to the
observer--bearing in one of two points diametrically opposite the small
disk of the sun, in the other the disk of the moon--runs a course equal
to the motion of the sun from the head or the tail of the dragon
(_Draco_). The other, of simple construction, marked with a small moon,
signifies in like manner the motion of the moon from the head or the
tail of the dragon.

Immediately below, there is a larger circle, common [referring] to both
these indices, which is divided into 12 parts. Each of these parts in
turn, in the outer periphery, is subd