The Vast Abyss Part 59

Tom gave proof of his readiness a few days later, when the broken windows had been replaced, fresh solutions made, and the village had again calmed down to its regular natural state of repose; for, upon his uncle proposing that they should proceed at once to silver the big speculum, he eagerly went off to the workshop to get all ready for his uncle's coming.

Short as the distance was though, he did not get away without encountering Pete, who hurried up to the wall to shout over at him--

"I know. Yer did shoot at me, but I shan't forget it, so look out."

Then hearing some one coming from the cottage, he ducked down like a wild animal seeking concealment, and hurried away.

Then the whole process was gone through to the smallest minutiae, and only an hour after the silvered face of the mirror was deluged with rain-water, and uncle and nephew gazed in triumph at their work, for there was no sign of greyish-drab powder about the mirror, and it was so bright that polishing seemed unnecessary.

The next day it was polished, till by a side light it looked black, while in face it was a brilliant looking-gla.s.s ready to reflect the faintest stars; and after being put away securely, the great tube was set about, and in due time this was lightly and strongly made of long laths hooped together. A shallow tray was contrived deep enough to hold the speculum, and fitted with screws, so that it could be secured to one end. Next followed the fitting of a properly-constructed eye-piece from a London optician, contrived so that it looked at right angles into a small reflector, which also had to be carefully fixed in the axis of the great speculum.

CHAPTER THIRTY TWO.

"What's the matter, Tom?" said Uncle Richard one day, as they were busy at work over the telescope, and Tom was scratching his head.

"There's nothing the matter, uncle, only I'm a bit puzzled."

"What about?"

"Over this great gla.s.s. It's going to be so different to the old one."

"Of course; that is a refractor, and this is going to be a reflector."

"Yes, uncle, but it seems so queer. The refractor is a tube made so that you can look through it, but the reflector will be, if you are right, so that you can't look through it, because instead of being at the end, the hole will be in the side. Is that correct?"

"Quite right, and you are quite wrong, Tom, for you do not understand the first simple truth in connection with a telescope."

"I suppose not, uncle," replied the lad, with a sigh. "I am very stupid."

"No, you are not, sir, only about as ignorant as most people are about gla.s.ses. I have explained the matter to you, but you have not taken it in."

"I suppose not, uncle," said Tom, wrinkling his brow.

"Then understand it now, once for all. It is very simple if you will try and grasp it. Now look here: what do you do with an ordinary telescope or opera-gla.s.s, single or double? Hold it up to your eyes, do you not?"

"Yes, uncle."

"And then?"

"Look through it at something distant, and it seems to draw it near."

"You do what?"

"Look through it, uncle."

"Nothing of the kind, sir, you do not."

Tom looked puzzled. What did his uncle mean? He had, he thought, looked through a pair of field-gla.s.ses scores of times at home in the old days.

"I make you stare, my lad, but I am glad to see it, for it shows me how right I am, and that you do think as everybody else does who has not studied optics, that you look through a gla.s.s at an object."

Tom stared harder, and once more the old idea came to him, and he asked himself whether there were times when his uncle did not quite understand what he was saying.

"But you do, uncle," he cried at last. Then he qualified this declaration by saying, "Don't you?"

"No, my boy, once for all you do not; and if you take up any telescope, and remove the eye-piece before looking along the tube, you will see that your eyes will not penetrate the gla.s.s at the end. Then if you try the eye-piece alone, you will find that you cannot even look through that. How much less then will you be able to look through both at once."

"But it seems so strange, uncle. You have a big magnifying-gla.s.s in a tube, and don't look through it? Then what do you do?"

"Certainly not look through it, my boy."

"But the bigger the gla.s.ses are the more they magnify--the moon, say."

"Yes, Tom; and the more light they gather."

"Well, then, why do you say, uncle, that you don't look through the gla.s.s?"

"Because it is a fact that I want you to understand," said Uncle Richard, smiling. "The big gla.s.s, or in our case the reflecting speculum, forms a tiny image of the object at which it is pointed, close to where we look in, within an inch or so of our eye."

"A tiny image, uncle?"

"Well, picture, then."

"But you say tiny! It looks big enough when we put our eye to the little round hole."

"To be sure it does. But what do you look through?"

"The eye-piece."

"Well, what is the eye-piece?"

"A little gla.s.s or two--lenses."

"These gla.s.ses or lenses form a microscope, Tom; and through them you look at the tiny image formed in the focus of the great lens or the speculum, whichever you use."

"But I thought microscopes were only used to magnify things invisible to the eye."

"Well, Jupiter's moons, Saturn's ring, and the markings on Mars are all invisible to the naked eye. So are the craters in the moon; so we use the big speculum to gather the light, and then look at the spot where all the rays of light come to their narrowest point, with an eye-piece which really is a microscope."

"But I don't understand now," said Tom uneasily. "I wish I was not so--"

"If you say stupid again, Tom, I shall quarrel with you," said Uncle Richard sternly. "I never think any boy is stupid who tries to master a subject. One boy's brain may be slower at acquiring knowledge than another, but that does not prove him to be stupid. What is it you don't follow?"

"About our telescope. If the light from the big speculum is all reflected nearly to a point, ought we not to look down at it?"

"No; because then our heads would be in the way, and would cast a shadow upon it. To avoid that, I put the little mirror in the middle, near the top, just at the right slant, so that the rays are turned off at right angles into the eye-piece, and so we are able to look without interrupting the light."