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DESCRIPTION OF THE PLATES.

§ 32. Plate I. Fig. 1. The flat back of the Astrolabe; see § 28.

Plate II. Fig. 2. The front of the Astrolabe, with raised border. In the wide depression in the middle, the plate called the 'Rete' is dropped in, and is shewn in its primary position. Other positions of it are sketched in Fig. 11 and Fig. 12.

Plate III. Fig. 3. The 'Rewle' carrying two sights, which revolved at the back of the Astrolabe. Astrol. i. 13.

Fig. 4. The central 'Pin,' shewn with the 'Wedge' inserted through it. Astrol. i. 14; cf. Fig. 7.

Fig. 5. One of the Tables or discs, used by being dropped within the depression on the front of the Astrolabe; i. 17. They were marked differently, according to the latitude of the place. The one here drawn is suitable for the latitude of Oxford, nearly.

Fig. 6. The 'Label,' which revolved at the front of the Astrolabe; i. 22.

Plate IV. Fig. 7. Another form of the 'Pin,' shewing the Wedge cut into the shape of a Horse (i. 14); from MS. Camb. Ii. 3. 3.

Fig. 8. Diagram, shewing how to draw the three 'principal circles'; see footnote on p. 183.

Fig. 9. Another form of the 'Rete,' from MS. Ii. 3. 3; cf. Fig. 2. This figure shews the 'Almury' very clearly; Astrol. i. 23.

Plate V. Fig. 10. Diagram of the nine spheres; from MS. Camb. Ii. 3. 3. Astrol. i. 17.

Fig. 11. Rough sketch of the position of the 'Rete' in Astrol. ii. 3 (first part). Denticle opposite C, and first point of Aries opposite X; 9 a.m.

[ lxxx ]Fig. 12. Rough sketch of the position of the 'Rete' in Astrol. ii. 3 (second part). Denticle near O; first point of Aries near H; 8h. 8m. p.m.

Fig. 13. Diagram of the Elevation of the Pole; Astrol. ii. 23. The arc AN is 56°; A′N is 48°; A′P is 4°; and PN is 52°. A, A′ are two positions of the Pole-star.

Plate VI. Fig. 14. A 'Table' or disc shewing the twelve astrological 'Houses'; Astrol. ii. 36 and 37.

Fig. 15. Diagram shewing how to ascertain the meridional line from two shadows of an upright gnomon; Astrol. ii. 38.

Fig. 16. Diagram illustrating the use of the Umbra Recta; Astrol. ii. 41, 41a, and 41b.

Fig. 17. Diagram of the use of the Umbra Versa, at two observations; Astrol. ii. 42, 42a, and 42b.

Fig. 18. Use of the Umbra Recta, at two observations; Astrol. ii. 43 and 43a.

Plate I

FIG. 1. BACK OF THE 'ASTROLABE.'

Plate II

FIG. 2. FRONT OF THE 'ASTROLABE.'

Plate III

FIG. 3. LABEL. FIG. 4. PIN. FIG. 5. PLATE FOR A CLIMATE.

FIG. 6. RULE.

Plate IV

FIG. 7. WEDGE AND HORSE (from a MS.).

FIG. 8. DIAGRAM FOR A PROPOSITION. FIG. 9. STAR-POINTS.

Plate V

FIG. 10. NINE SPHERES. FIGS. 11, 12, 13. PROBLEMS.

Plate VI

FIG. 14. HOUSES. FIGS. 15-18. UMBRA RECTA AND UMBRA VERSA.