Footnote 46
Part II, §20.  Here the disc (fig. 5) is supposed to be placed beneath the Rete (fig. 2).  The probosition merely tells us that the difference between the meridian altitudes of the given degree of the zodiac and of the 1st point of Aries is the declination of that degree, which follows from the very definition of the term.  There is hardly any necessity for setting the second prick, as it is sufficiently marked by being the point where the equinoctial circle crosses the south line.  If the given degree lie outside this circle, the declination is south; if inside, it is north.