by four-place logarithms (using the approximate values for φ, _t_, and _h_, since these are quite sufficiently accurate for the purpose) and inserted into the three star-equations.[66] By then solving the three simultaneous equations for _d_φ, the required correction to the assumed latitude was at once obtained. As the method is one not usually treated of in books on practical astronomy, I give on the following pages the reduction of an observation worked out in full. _Latitude by Equal Altitudes of Three Stars._ Station on Gebel Um Heshenib. January 30, 1906. Approximate φ = 24° 20′ 50″ N. „ λ = 34° 51′ 0″ E. Sidereal watch U. and C. 30811, approximately 2m 22s fast on L.S.T., rate negligible. Observed times of equal altitudes by watch:— _Polaris_ 3h 33m 54s·2 α _Columbæ_ 3 42 40 ·8 ε _Canis majoris_ 4 24 35 ·8 _Polaris._ Watch time 3h 33m 54s·2 Watch fast 2 22 ·0 ------------ L.S.T. 3 31 32 ·2 Star’s R.A. 1 25 9 ·1 ------------ _t_ 2 6 23 ·1 = 31° 35′ 46″·5 W. of meridian. ------------ - φ = 24° 20′ 50″ log sin 1·6151769 - δ = 88° 48′ 33″·1 log sin 1·9999062 --------- - - 1·6150831 log cos δ 2·3177 - Nat. (1) 0·4121764 log sin _t_ 1·7193 --------- ------ - 2·0370 - - φ = 24° 20′ 50″ log cos 1·9595488 log cos _h_ 1·9560 ------ - - δ = 88° 48′ 33″·1 log cos 2·3176870 log sin _A_ 2·0810 - - _t_ = 31° 35′ 46″·5 log cos 1·9303179 log cos φ 1·9595 --------- ------ - 2·0405 - - 2·2075537 Nat. = 0·011 --------- Nat. (2) 0·0161270