Footnote 29
Part II, §3.  Drop the disc (fig. 5) within the border of the mother, and the Rete over it.  Take the sun's altitude by §2, and let it be 25½°.  As the altitude was taken by the back of the Astrolabe, turn it over, and then let the Rete revolve westward till the 1st point of Aries is just within the altitude-circle marked 25, allowing for the ½ degree by guess.  This will bring the denticle near the letter C, and the first point of Aries near X, which means 9 A.M.  At the same time, the 20th degree of Gemini will be on the horizon obliquus.  See fig. II, Plate V.  This result can be approximately verified by a common globe thus; elevate the pole nearly 52°; turn the small brass hour-circle so that the figure XII lies on the equinoctial colure; then turn the globe till IX lies under the brass meridian.  In the next example, by the Astrolabe, let the height of Alhabor (Sirius) be about 18°.  Turn the denticle Eastward till it touches the 58th degree near the letter O, and it will be found that Alhabor is about 18° high among the almicanteras, whilst the first point of Aries points to 32° near the letter H, i.e. to 8 minutes past 8 P.M.; whilst at the same time, the 23rd degree of Libra is almost on the Horizon obliquus on the Eastern side.  By the globe, at about 8 minutes past 8 P.M., the altitude of Sirius is very nearly 18°, and the 23rd of Libra is very near the Eastern horizon.  See fig. 12, Plate V.