The Brick Moon
[From the papers of Captain FREDERIC INGHAM.]
I
PREPARATION
I have no sort of objection now to telling the whole story. The subscribers, of course, have a right to know what became of their money. The astronomers may as well know all about it, before they announce any more asteroids with an enormous movement in declination. And experimenters on the longitude may as well know, so that they may act advisedly in attempting another brick moon or in refusing to do so.
It all began more than thirty years ago, when we were in college; as most good things begin. We were studying in the book which has gray sides and a green back, and is called "Cambridge Astronomy" because it is translated from the French. We came across this business of the longitude, and, as we talked, in the gloom and glamour of the old South Middle dining-hall, we had going the usual number of students' stories about rewards offered by the Board of Longitude for discoveries in that matter,-- stories, all of which, so far as I know, are lies. Like all boys, we had tried our hands at perpetual motion. For me, I was sure I could square the circle, if they would give me chalk enough. But as to this business of the longitude, it was reserved for Q.[1] to make the happy hit and to explain it to the rest of us.
[1] Wherever Q. is referred to in these pages my brother Nathan is meant. One of his noms de plume was Gnat Q. Hale, because G and Q may be silent letters.
I wonder if I can explain it to an unlearned world, which has not studied the book with gray sides and a green cambric back. Let us try.
You know then, dear world, that when you look at the North Star, it always appears to you at just the same height above the horizon or what is between you and the horizon: say the Dwight School-house, or the houses in Concord Street; or to me, just now, North College. You know also that, if you were to travel to the North Pole, the North Star would be just over your head. And, if you were to travel to the equator, it would be just on your horizon, if you could see it at all through the red, dusty, hazy mist in the north, as you could not. If you were just half-way between pole and equator, on the line between us and Canada, the North Star would be half-way up, or 45@ from the horizon. So you would know there that you were 45@ from the equator. Then in Boston, you would find it was 42@ 20' from the horizon. So you know there that you are 42@ 20' from the equator. At Seattle again you would find it was 47@ 40' high, so our friends at Seattle know that they are at 47@ 40' from the equator. The latitude of a place, in other words, is found very easily by any observation which shows how high the North Star is; if you do not want to measure the North Star, you may take any star when it is just to north of you, and measure its height; wait twelve hours, and if you can find it, measure its height again. Split the difference, and that is the altitude of the pole, or the latitude of you, the observer.
"Of course we know this," says the graduating world. "Do you suppose that is what we borrow your book for, to have you spell out your miserable elementary astronomy?" At which rebuff I should shrink distressed, but that a chorus of voices an octave higher comes up with, "Dear Mr. Ingham, we are ever so much obliged to you; we did not know it at all before, and you make it perfectly clear."
Thank you, my dear, and you, and you. We will not care what the others say. If you do understand it, or do know it, it is more than Mr. Charles Reade knew, or he would not have made his two lovers on the island guess at their latitude, as they did. If they had either of them been educated at a respectable academy for the Middle Classes, they would have fared better.
Now about the longitude.
The latitude, which you have found, measures your distance north or south from the equator or the pole. To find your longitude, you want to find your distance east or west from the meridian of Greenwich. Now, if any one would build a good tall tower at Greenwich, straight into the sky,--say a hundred miles into the sky,--of course if you and I were east or west of it, and could see it, we could tell how far east or west we were by measuring the apparent height of the tower above our horizon. If we could see so far, when the lantern with a Drummond's light, "ever so bright," on the very top of the tower, appeared to be on our horizon, we should know we were eight hundred and seventy-three miles away from it. The top of the tower would answer for us as the North Star does when we are measuring the latitude. If we