Astronomy for the use of schools and academies (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908, Rolfe, W. J. (William James), 1827-1910 · New York : Potter, Ainsworth, & Co. · leaf 52
Fig. 39- to year. It will be seen, from Figs. 3S and 39, that thedeclination is also slowly changing. 30. Nutation. — The gyratory motion of the earths axisis not perfectly regular and uniform. The earths axis has ASTRONOMY. 35 … a slight tremulous motion, oscillating to and fro through ashort distance once in about nineteen years. This tremu-lous motion of- the axis causes the pole of the heavens todescribe an undulating curve, as shown in Fig. 40, andgives a slight unevenness to the motion of the equinoxesalong the…
Astronomy
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