Rollo's Experiments Part 10

"And the rest of the stars," said Rollo, "do they go round too?"

"Yes," said Jonas; "only they are so far from the North Star, that they go in larger circles, and so go down below the horizon, and are out of sight sometimes. They come up in the east, like the sun, and go over and down in the west. But they don't go over straight," he added. "They don't come right up straight; and so go directly over. They slant away, off to the south, so as to keep always just so far from the North Star."

"That's curious," said Rollo.

"I think it is," said Jonas. "And they all go together; they don't move about among themselves, at all."

"Don't they?" said Rollo.

"No," said Jonas; "only there are a few wandering stars, that keep wandering about among the others. But the rest all keep exactly in their places, and all go round together; so they are called _fixed_ stars."

"Show me one of the wandering stars," said Rollo.

"I don't know which they are," said Jonas, "only they are pretty bright ones."

"I guess that's one," said Rollo, pointing to a pretty bright star in the east.

"Perhaps it is," said Jonas.

"I wish I knew," said Rollo.

"I'll tell you how you can find out," said Jonas.

"How?" asked Rollo.

"Why, when you go into the house, take a piece of paper, and go to the window, and make some dots upon it, for all the stars around that one.

Make the dots just in the places that the stars seem to be in. Then let them all go. They will rise more and more, and go overhead, and down in the west, and to-morrow night they will come up in the east again; and then you can look at them again, and see if the bright star has changed its place at all."

Rollo said that he meant to do that; and then he said that he began to feel cold, and wanted to go in. But Jonas told him that he ought to wait and help finish the dial.

So they went to the place which Jonas had selected, and Jonas, looking up first at the North Star, made a hole in the ground, with an iron bar, in an oblique direction, so that the bar should point pretty nearly to the North Star. Then he drove in one of his stakes in the same way. He then made a hole, perpendicularly, directly under the end of this inclined stake, and drove the other stake down into that. The two upper ends of the stakes were now together.

Then Jonas stooped down, so as to bring his eye near the edge of the inclined stake, at the lower end, so that he could "_sight_" along the edge of it, towards the star. He had previously cut a notch in it, so that he could get his eye down far enough to look directly along the edge. At the same time, Rollo took hold of the upper end, and stood ready to move it either way, as Jonas might direct, until it should point exactly towards the North Star.

"Down," said Jonas.

Then Rollo moved it a little down.

"Down more."

Rollo moved it farther.

"Up--up a little," added Jonas. "There--that will do. Now hold the two stakes firmly together, exactly so."

Then Jonas took some nails, which he had before provided, and nailed the tops of the stakes together, Rollo holding the axe up against them, on the opposite side. This supported the end of the inclined stake firmly, so that it could not move up or down. This was all that the boys wanted to do in the evening, and so they both went in.

The next day, Jonas sawed off the ends of both stakes where they projected beyond the junction; and then Rollo said he would watch the clock all day, and mark the place where the shadow came each hour, and drive a little stake down. "Then," said he, "our dial will be done."

"But what do you suppose is the reason," said Rollo, "that we must make it point to the North Star more than to any other?"

"I don't know," said Jonas, "unless it is because the North Star is the only one that keeps always in the same place. The rest move round and round every day. Those that are far enough from the North Star to go down below the horizon, rise and set; and those that are not far enough, go round and round in circles, in the open sky. But the North Star keeps still."

"Does it?" said Rollo, turning around, and looking up to the part of the heavens where he had seen the star the evening before.

"Yes," said Jonas; "and the reason why we cannot see it now, is the bright daylight. It is up there now, just where it was last night."

"And the Dipper, too?" said Rollo.

"Yes, and the Dipper, too; only that has moved half round, I suppose, and is now away up above the North Star."

"I wish I could see it," said Rollo. And he looked as steadily and intently into the clear blue sky, as he could; but he could not possibly see the least sign of a star.

However, the sun shone bright, and it cast a strong shadow from the stakes which they had driven into the ground. Jonas soon went away to his work, and left Rollo to mark the hours by means of the clock.

So Rollo had to go into the house very often to see what time it was; and at last his father, who was sitting there at his writing, asked him what made him want to see the clock so much. Rollo told him the reason.

So his father put down his pen, and came out to see the dial.

When he saw the two stakes, with their lower ends driven into the ground, and the upper ends nailed firmly together, he looked at them with a smile, but did not say any thing.

"Will that do?" said Rollo, looking up very eagerly into his father's face.

His father did not answer, but continued to examine the work on all sides, with a countenance expressive of curiosity and pleasure.

"It points to the North Star, exactly," added Rollo. "Jonas _sighted_ it."

"Yes," said his father; "I think that will do; you have got quite a respectable _gnomon_."

"Gnomon?" said Rollo.

"Yes," said his father; "we call such a thing a gnomon. In common dials, they are made of bra.s.s; but I don't see why this won't do very well. It is rather a _large_ gnomon."

"Is it?" said Rollo.

"Yes," said his father, "I think it is the biggest gnomon I ever saw.

"But how are you going to mark the hour lines, Rollo?" asked his father.

"Why, we are going to drive little stakes down into the ground."

"'Seems to me that you can contrive some better plan than that," said his father.

"Why?" said Rollo. "Is not that a good plan?"

"Not very good," he replied; "because you cannot be exact in driving down stakes. The beauty of a dial is its exactness. I should think that you would do better to put a board down upon the ground, and mark your lines upon that."

"O, the board would get knocked about," said Rollo.