Note 20 — Chapter XXI · THE ADJUSTMENTS OF THE EQUATORIAL.
Reading edition
This error varies as the tangent of the declination, and therefore to find the constant for the instrument, in case the parts do not admit of easy adjustment, we divide 4m. 1s. by 1·18 the tan. of Dec. of η Ursæ Majoris, giving 3 min. 28 sec.