Davies, Charles, 1798-1876 · New York, Cincinnati [etc.] American book company · leaf 383
; the arm ismoved over the surface of the declination arc, and its vernier set to any read-ing by turning the head of the tangent screw k. It is also securely clampedin any position by a screw, concealed in the engraving. Solar Lenses and Lines.—At each end of the arm, h, is a rectangu-lar block of… … On the surface of the plate are marked two sets oflines intersecting each other at right angles ; of these h b are termed the hour lines, and c c the equatorial lines,, as /> rrjhaving reference respectively to the hour of the day and ^ ■ the position of the sun in relation to the equator. Fig.…
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