Part 12 (1/2)
”The True Course is the angle made with the meridian by a straight line on the chart drawn to connect the s.h.i.+p's position with the place bound to.”
Just what I wanted. The _Snark's_ position was at the western entrance of the pa.s.sage between Viti Levu and Mbengha. The immediate place she was bound to was a place on the chart ten miles north of Vatu Leile. I p.r.i.c.ked that place off on the chart with my dividers, and with my parallel rulers found that west-by-south was the true course. I had but to give it to the man at the wheel and the _Snark_ would win her way to the safety of the open sea.
But alas and alack and lucky for me, I read on. I discovered that the compa.s.s, that trusty, everlasting friend of the mariner, was not given to pointing north. It varied. Sometimes it pointed east of north, sometimes west of north, and on occasion it even turned tail on north and pointed south. The variation at the particular spot on the globe occupied by the _Snark_ was 9 40' easterly. Well, that had to be taken in to account before I gave the steering course to the man at the wheel.
I read:
”The Correct Magnetic Course is derived from the True Course by applying to it the variation.”
Therefore, I reasoned, if the compa.s.s points 9 40' eastward of north, and I wanted to sail due north, I should have to steer 9 40' westward of the north indicated by the compa.s.s and which was not north at all. So I added 9 40' to the left of my west-by-south course, thus getting my correct Magnetic Course, and was ready once more to run to open sea.
Again alas and alack! The Correct Magnetic Course was not the Compa.s.s Course. There was another sly little devil lying in wait to trip me up and land me smas.h.i.+ng on the reefs of Vatu Leile. This little devil went by the name of Deviation. I read:
”The Compa.s.s Course is the course to steer, and is derived from the Correct Magnetic Course by applying to it the Deviation.”
Now Deviation is the variation in the needle caused by the distribution of iron on board of s.h.i.+p. This purely local variation I derived from the deviation card of my standard compa.s.s and then applied to the Correct Magnetic Course. The result was the Compa.s.s Course. And yet, not yet.
My standard compa.s.s was amids.h.i.+ps on the companionway. My steering compa.s.s was aft, in the c.o.c.kpit, near the wheel. When the steering compa.s.s pointed west-by-south three-quarters-south (the steering course), the standard compa.s.s pointed west-one-half-north, which was certainly not the steering course. I kept the _Snark_ up till she was heading west-by-south-three-quarters-south on the standard compa.s.s, which gave, on the steering compa.s.s, south-west-by-west.
The foregoing operations const.i.tute the simple little matter of setting a course. And the worst of it is that one must perform every step correctly or else he will hear ”Breakers ahead!” some pleasant night, a nice sea-bath, and be given the delightful diversion of fighting his way to the sh.o.r.e through a horde of man-eating sharks.
Just as the compa.s.s is tricky and strives to fool the mariner by pointing in all directions except north, so does that guide post of the sky, the sun, persist in not being where it ought to be at a given time. This carelessness of the sun is the cause of more trouble-at least it caused trouble for me. To find out where one is on the earth's surface, he must know, at precisely the same time, where the sun is in the heavens. That is to say, the sun, which is the timekeeper for men, doesn't run on time.
When I discovered this, I fell into deep gloom and all the Cosmos was filled with doubt. Immutable laws, such as gravitation and the conservation of energy, became wobbly, and I was prepared to witness their violation at any moment and to remain unastonished. For see, if the compa.s.s lied and the sun did not keep its engagements, why should not objects lose their mutual attraction and why should not a few bushel baskets of force be annihilated? Even perpetual motion became possible, and I was in a frame of mind p.r.o.ne to purchase Keeley-Motor stock from the first enterprising agent that landed on the _Snark's_ deck. And when I discovered that the earth really rotated on its axis 366 times a year, while there were only 365 sunrises and sunsets, I was ready to doubt my own ident.i.ty.
This is the way of the sun. It is so irregular that it is impossible for man to devise a clock that will keep the sun's time. The sun accelerates and r.e.t.a.r.ds as no clock could be made to accelerate and r.e.t.a.r.d. The sun is sometimes ahead of its schedule; at other times it is lagging behind; and at still other times it is breaking the speed limit in order to overtake itself, or, rather, to catch up with where it ought to be in the sky. In this last case it does not slow down quick enough, and, as a result, goes das.h.i.+ng ahead of where it ought to be. In fact, only four days in a year do the sun and the place where the sun ought to be happen to coincide. The remaining 361 days the sun is pothering around all over the shop. Man, being more perfect than the sun, makes a clock that keeps regular time. Also, he calculates how far the sun is ahead of its schedule or behind. The difference between the sun's position and the position where the sun ought to be if it were a decent, self-respecting sun, man calls the Equation of Time. Thus, the navigator endeavouring to find his s.h.i.+p's position on the sea, looks in his chronometer to see where precisely the sun ought to be according to the Greenwich custodian of the sun. Then to that location he applies the Equation of Time and finds out where the sun ought to be and isn't. This latter location, along with several other locations, enables him to find out what the man from Kansas demanded to know some years ago.
The _Snark_ sailed from Fiji on Sat.u.r.day, June 6, and the next day, Sunday, on the wide ocean, out of sight of land, I proceeded to endeavour to find out my position by a chronometer sight for longitude and by a meridian observation for lat.i.tude. The chronometer sight was taken in the morning when the sun was some 21 above the horizon. I looked in the Nautical Almanac and found that on that very day, June 7, the sun was behind time 1 minute and 26 seconds, and that it was catching up at a rate of 14.67 seconds per hour. The chronometer said that at the precise moment of taking the sun's alt.i.tude it was twenty-five minutes after eight o'clock at Greenwich. From this date it would seem a schoolboy's task to correct the Equation of Time. Unfortunately, I was not a schoolboy. Obviously, at the middle of the day, at Greenwich, the sun was 1 minute and 26 seconds behind time. Equally obviously, if it were eleven o'clock in the morning, the sun would be 1 minute and 26 seconds behind time plus 14.67 seconds. If it were ten o'clock in the morning, twice 14.67 seconds would have to be added. And if it were 8: 25 in the morning, then 3 times 14.67 seconds would have to be added. Quite clearly, then, if, instead of being 8:25 A.M., it were 8:25 P.M., then 8 times 14.67 seconds would have to be, not added, but _subtracted_; for, if, at noon, the sun were 1 minute and 26 seconds behind time, and if it were catching up with where it ought to be at the rate of 14.67 seconds per hour, then at 8.25 P.M. it would be much nearer where it ought to be than it had been at noon.
So far, so good. But was that 8:25 of the chronometer A.M., or P.M.? I looked at the _Snark's_ clock. It marked 8:9, and it was certainly A.M.
for I had just finished breakfast. Therefore, if it was eight in the morning on board the _Snark_, the eight o'clock of the chronometer (which was the time of the day at Greenwich) must be a different eight o'clock from the _Snark's_ eight o'clock. But what eight o'clock was it? It can't be the eight o'clock of this morning, I reasoned; therefore, it must be either eight o'clock this evening or eight o'clock last night.
It was at this juncture that I fell into the bottomless pit of intellectual chaos. We are in east longitude, I reasoned, therefore we are ahead of Greenwich. If we are behind Greenwich, then to-day is yesterday; if we are ahead of Greenwich, then yesterday is to-day, but if yesterday is to-day, what under the sun is to-day!-to-morrow? Absurd!
Yet it must be correct. When I took the sun this morning at 8:25, the sun's custodians at Greenwich were just arising from dinner last night.
”Then correct the Equation of Time for yesterday,” says my logical mind.
”But to-day is to-day,” my literal mind insists. ”I must correct the sun for to-day and not for yesterday.”
”Yet to-day is yesterday,” urges my logical mind.
”That's all very well,” my literal mind continues, ”If I were in Greenwich I might be in yesterday. Strange things happen in Greenwich.
But I know as sure as I am living that I am here, now, in to-day, June 7, and that I took the sun here, now, to-day, June 7. Therefore, I must correct the sun here, now, to-day, June 7.”
”Bos.h.!.+” snaps my logical mind. ”Lecky says-”
”Never mind what Lecky says,” interrupts my literal mind. ”Let me tell you what the Nautical Almanac says. The Nautical Almanac says that to-day, June 7, the sun was 1 minute and 26 seconds behind time and catching up at the rate of 14.67 seconds per hour. It says that yesterday, June 6, the sun was 1 minute and 36 seconds behind time and catching up at the rate of 15.66 seconds per hour. You see, it is preposterous to think of correcting to-day's sun by yesterday's time-table.”
”Fool!”