Page 153

"bound south", and on Dec. 21st it begins all over again. (Page 152)

Consequently, the sun has a different position as regards the equator for every day in the year and every hour in the day for that matter. This position is very carefully figured out for every day and hour by the national astronomers, and printed in a "nautical almanac” with which every ship captain is supplied. The position of the {sun} as regards the equator is called the "declination" Declination 23° N., for example, means that the [sun] is 23° N. of the equator on that particular day and time.

Now, if you know how far the [sun] is N of the Equator, and know also how far you are N. of the sun, the latitude is found as easily as adding 2 and 2. The navigator knows from his almanac where the [sun] is regards the equator. He finds where he is regards the [sun] by means of an instrument called the sextant. 

Just before 12 o'clock he takes his stand on deck, faces the sun, and squints through the telescope of his sextant at the horizon. He sees the horizon as a perfect distinct line through one half of a little square of glass. (page 152). The other half of this class is silvered: it is a mirror. There is another mirror on the instrument at the end of the swing arm, and the second mirror reflects the image of the [sun]. Now the captain move the arm slowly until the second mirror is tipped just enough to throw the reflection of the [sun] into the first mirror. Dark glasses shield the eyes from the glare, and the captain can see two things – the horizon through the plain glass, and the image of the sun in the mirrored. He brings that image down by gently moving the arm until the lower edge of it just touches the horizon. For a few moments before noon, as the [sun] continues to rise in the heavens, the motion of the swinging arm continues to

(Cont’d)