Hogben. — Night Marching by the Stars. 513 



Art. XL VIII. — Night Marching by the Stars. 

 By George Hogben, M.A., F.G.S., C.M.G. 



[Read before the Wellington Philosophical Society, 1st November, 1916 ; received by 

 Editors, 30th December, 1916; issued separately, 10th December, 1917.] 



Marching or sailing the ocean by the stars is, of course, no new thing ; in 

 fact, owing to the use of the compass the method is less used in modern 

 times than it was of old. But there are many occasions on which the 

 compass is out of order, or not available ; besides, only a few officers 

 can be provided with compasses, and oftentimes it falls to the lot of the 

 individual non-commissioned officer or private to determine his direction 

 for himself. It is then that a little star knowledge may be most useful. 



The first method described below is that recommended to the members 

 of the New Zealand Expeditionary Forces, who have been provided with 

 copies of star maps 1 and 2, with brief directions for their use. Star map 

 No. 1 is familiar to every one ; the diagram called star map No. 2 is, I 

 believe, new. What it enables any one to do, on any clear night, is to find 

 the south approximately at any hour on any day of the year. 



I am well aware that other methods have been used or recommended 

 for use. The chief of these were discussed in connection with a paper read 

 before the Royal Geographical Society of London by Mr. E. A. Reeves, 

 on the 13th April, 1916.* The two most important are (i) by the use of 

 Colonel Tilney's tables, which give the bearings of certain selected con- 

 spicuous stars for the local mean time ; (ii) by the finding of the alti- 

 tude of a known star above the horizon, and hence inferring its bearing 

 east or west of the meridian — this method being independent of the 

 date or hour. 



My second method, described below, is a modification of Colonel Tilney's, 

 as will be seen. The first method I have described is subject to an 

 important error due to the varying value of the equation of time at dif- 

 ferent periods of the year. Accordingly, in Table I, to be used in connection 

 with my second method, the approximate time of meridian transit given 

 for the first day of each month is calculated according to the average value 

 of the equation of time for the month. The error is thus greatly reduced. 



The simplest way in which I can explain the methods now presented 

 is to give the description as it would be given to an officer who wished to 

 use these methods in the field. 



Star Map No. 1 (looking North). 

 To find the North at any Time when the Stars are Visible. 



The two "Pointers" in the Great Bear (Ursa Major) point very nearly 

 to the North Pole of the sky, which is always due north of you. The 

 distance of the nearer " Pointer " from the North Pole is about five times 

 the distance between the two " Pointers." (There is a small star, Polaris, 

 near the Pole.) The two bright stars, Vega and Capella, nearly on opposite 



* Oeog. Joum., vol. xlvii, June 1916. pp. 440-60. 

 17— Trans 



