How to Tell the Time by Compass

Southland Times, Issue 22999, 19 September 1936, Page 21 (Supplement)

How to Tell the Time by Compass

(By B. W. Collins)

It is the apparent movement of the sun across the sky which gives us day and night, and from which we really derive our idea of time. Although there are all kinds of ways used or formerly used to measure time —such as clocks of many varieties, sand-glasses, water-clocks, etc.—it is, of course, still possible to measure our time directly from the sun. One way of doing this is by the sun-dial; but a very much simpler one is by means of a compass. With this instrument we can find the direction of the sun, and knowing its direction at certain times of the day we can calculate by proportion the time of our observation. Thus, suppose we found that the sun was north-north-west, that is, 22$ degrees west of north. From the table given below we see that at noon the sun is due north and at 3 o’clock it is north-west. North-north-west is just half-way between these two distances, and so the time was half way between 12 and 3, that is 1.30 p.m.

The directions given below are true only for the southern hemisphere. In the northern hemisphere at noon the sun is due south instead of north. Also, it is necessary to remember that the compass needle does not point to true north, but to magnetic north, which is about 17 degrees east of this for

Christchurch and the surrounding districts. Usually compasses are made in a foreign country and have magnetic north marked for that country, not for New Zealand. Time. Direction of Sun, 6 a.m East 9 a.m North-east 12 noon .. .. North 3 p.m North-west 6 p.m West 9 p.m South-west September When the year began in March, September was the seventh month of the year—hence its name September from the Latin word Septimus or seventh. When the new year was put back two months, September became the ninth month. October became the tenth month, November the eleventh month and December the twelfth month. Julius Caesar gave September 31 days when he reformed the calendar, but Augustus took the extra day away when he reformed the calendar some time after. The Saxons called September, Gerst monat, or barley month, because it was the month during which they harvested their barley. ; • QUESTIONS Readers are invited to send questions on any subjects of interest to be answered in these columns.