USS Badger Spanish American War Ship's Log

 …swing, will point approximately N and S. (Notice that approximately) it may be news to you that there are only a very few places on the globe where the compass points directly to the North Pole. In the lat. of the U.S. the needle points considerably to the W. of the true N., and this "variation”, as it is called; changes materially with material changes at this ship's position, and even at the same spot, it is not the same every year. This variation must be allowed for when the "skipper" takes his course. A compass, anyway, is an uncertain and delicate contrivance. Theoretically, all the compass on earth point to the same spot. Practically, no two compasses point alike on ship board, for each has certain local influences that tend to make it "deviate" as it is called, from the common point. Masses of [?], chains, wire rope, even an awning post, near the compass, affects it’s pointing, and affect it differently, in every position of the ship's head. In...

But this method of "dead reckoning” while well enough for coactevise voyaging, where known marks are frequently seen, is prolific of error. Mistakes are continuous, and cumulative. The mistake of one day is carried to the next, and unless there is a frequent method of "checking" the position, the best captain is likely to be uncertain of his exact location after a day or two. By little and little, as astronomers figured the movements of the heavenly bodies more accurately, and, as instrumental makers improved the reliability of their appliances, the Mariners used more, and more, the observation method, that is, the determination of his position by figuring it from the known positions of the sun, moon, or a star. He very early learned to find his latitude by this method, but it was a long time before he could find his longitude as well. First, as to getting the latitude. Latitude, you remember, is simply one's distance from the equator, measured in [degrees], [feet] a...

Diagram illustrating declination of the [sun]: that is, its distance from the Equator during the year. Navigator finds his lat. by finding with his sextant his distance from the [sun] and + to or - from the known distance of the [sun] N. or S. of the equator at that day and hour.

"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 throu...

keep the image in place, just "kissing" the horizon line. Finally, the upward movement of the [sun] ceases, there is a slight period of appent rest, and then it begins to descend toward the W. At that instant the captain says "Eight bells”, which means 12 o'clock noon. It is always noon, as you know, when the sun is at its highest point. The captain has now found two things. He has found the exact second of noon for his locality, and the index of his sextant tells him just how many degrees above the horizon the sun was at that second. The diagram will make this plain.   A - Captain D - Sun B - Horizon   C - Zenith - (spot in the heavens which is directly overhead) The angle C.B.A is a right angle, therefore the arc C.B. Is a quarter circle of 90°. We will suppose the Captain's sextant shows that the arc from the [sun] to the horizon – from D to B - is 40°. Then the distance from [sun] to Z must be the difference between 40° and 90°, which is 50° – savvy? Conseque...

 Diagram:

...he must get his longitude, also, and this, if he chooses, he can find from the same sextant sight, by means of his chronometer.   (A chronometer is a very fine and adjusted clock. One Harrison, by inventing a clock that would keep accurate time in all temperatures, and under all circumstances, received in 1773, a reward of $100.000 offered in the reign of Queen Anne for the best method of finding a ship longitude. The method is simplicity itself, in theory, and theories are all we are after now) You know, of course, that the earth revolves on its axis once in each 24 hours. As the earth turns from the W. to E. and the meridians of long. run N. and S., you can see that the 360° line of longitude passes under the [sun] one after the other, in 24 hours. And that means that a new degree passes every 4 minutes. Now, it is noon at any place on the earth when the [sun] is at the highest point in the heavens at that place. That is, it is noon at any place when the meridian, which passes...