Fresh emery out of the bottle was applied, moistened a little more, and the grinding went on for a while. Then there was a fresh washing, more of the coa.r.s.e emery applied, and so the task went on hour after hour that day and the next, when in the afternoon when the zinc mould was applied to the surface it fitted in almost exactly, and Tom gave a cheer.

"Yes, that will do," said Uncle Richard, whose face glowed with the exertion.

"What next then?" said Tom eagerly.

"The next grade of emery, boy," was the reply; "our task is of course now not to grind the speculum deeply, but to grind out all these scratches till it is as limpid as the surface of pure water."

"Don't look possible," said Tom. "Well, we will try."

The next morning they worked for an hour before breakfast in precisely the same way, gave a couple of hours to the task after breakfast, two more in the afternoon, and one in the evening--"a regular muscle-softener," Uncle Richard called it; but when for the last time the finely-ground emery number two was washed off, and the speculum examined, its surface looked much better, the rougher scratchings having disappeared.

Tom was all eagerness to begin the next day, when the number three emery was tried in precisely the same way. Then came work with the number four, very little of which was used at a time; and when this was put aside for number five, Tom again cheered, for the concave surface had become beautifully fine.

"Two more workings, and then the finishing," said Uncle Richard. "Think we shall polish out all the scratchings?"

"Why, they are gone now," cried Tom.

"Yes, it shows what patience will do," said Uncle Richard; "a man can't lift a house all at once, but he could do it a brick at a time."

The speculum was carefully placed aside after its cleansing, and the pair of amateur opticians locked up the place after hanging up their ap.r.o.ns.

"Wouldn't do to break that now, Tom, my boy."

"Break it?" cried the boy; "oh, it would be horrible. Why, we should have to make another, and go through all that again."

"Yes, Tom, but we could do it. I know of a gentleman who made a hundred of these specula with his own hands. But there will be something more interesting for you to see to-morrow."

"What, shall we get it done?"

"By no means; but first thing of all I must test it, and to do this easily, we must be up early when the sun is shining in at the east window of our workshop. Do you think you can call me by five?"

"I'm sure of it, uncle," cried Tom.

CHAPTER FIFTEEN.

Tom kept his word, for he started into wakefulness in the grey dawn out of an uncomfortable dream, in which he had seen the unfinished speculum fall off the bench on to the stone-floor, roll like a wheel out of the door, down the slope to the gate, bound over, and then go spinning down the lane and across the green, straight for the ragstone churchyard wall, where it was shivered to pieces.

"Only a dream," he said, as he leaped out of bed, ran to the window, and saw by the church clock that it was only half-past four.

"Time to go over and see if it is all right," he said, as he finished dressing, "and then come back and call uncle."

Going down-stairs, he took the keys of the mill from where they hung by the front door, went out into the garden, unlocked the gate, and went across to the mill, where, on peering through the window, he could see the gla.s.s lying just as it had been left.

"That's all right," said Tom; and he walked round by the back of the tower to see how the flowers and shrubs looked, when, to his startled surprise, he found footprints made by a heavy, clumsy pair of boots on the border beneath the wall.

Their meaning was plain enough. Some one had walked along there, and got out of the yard over the wall, while, upon a little further search, he found the spot where whoever it was had entered the yard by jumping down, the prints of two heels being deeply-marked in the newly-dug earth.

"That must have been Pete," said Tom, flushing; and he looked over the wall, half expecting to see the slouching figure of the lad.

But there was no one within sight, and he looked round the yard in search of the visitor's object. There was nothing but the old millstones stealable, and they stood here and there where they had been leaned against tower and wall; and at ten minutes to five, after noting that the sun was shining brightly, Sam went back to his uncle and called him, and at half-past five they went together to the mill-yard, where the footprints were pointed out.

"Have to keep the door carefully locked, Tom," said Uncle Richard.

"Hah! capital! the sun will be shining right through that window in a few minutes."

They entered the workshop, where a bench was drawn opposite to the last window, and about twelve feet away. To this, with Tom's help, the partly-polished speculum was borne.

"Not very bright for a reflector, Tom," said Uncle Richard. "What am I to do to make it brighter?"

"Go on polishing, uncle."

"Ah, but I want to test it this morning, to see if we have a good curve," said Tom's elder, smiling. "Fill the sponge with clean water and bring it here."

This was done, and the finely-ground surface was freely wetted, with the effect that it became far more luminous directly.

"Now, Tom," said his uncle, "I'm going to show you something in reflection. The sun is not quite high enough for the speculum, so give me that piece of looking-gla.s.s."

This was handed to him, and he held it on high, so that the low-down sun shone into it, and a reflection was cast from it back upon the wall just above the window.

"See that?"

"Yes, uncle. Done that many a time. Used to call it making jack-o'-lanterns."

"Well, that is the effect of a reflection from a flat or plane surface; the rays of light strike back at the same angle as they hit the surface.

Now then, I'll show you what happens from a curved surface."

He pa.s.sed the sponge rapidly over the ground speculum again, so as to glaze it--so to speak--with water, raised it upon its edge with the carefully-ground face directed at the window just as the sun rose high enough to shine in; and then by turning the great mirror slightly, the light reflected from it struck upon the wall at the side of the window.

"Now, Tom, what do you see?"

"A round spot of light about as big as a two-shilling piece," said the boy.

"Yes; all the rays of light which fall upon our mirror, gradually drawn together to where they form an image of the sun. It is only dull, my boy, but so far finely perfect, and we can say that we have gone on very successfully."

As he spoke he laid the mirror down upon its back.

"Is that all you are going to do?" asked Tom.

"Yes; I can test it no better till it is more advanced, my boy. It may seem a little thing to you, but it is enough to show me that we may go on, and not begin our work all over again. Now for a good turn until breakfast-time. Two good hours' work ought to produce some effect."

The lower disc, now become convex, was wetted and lightly touched over with number five emery, which seemed soft enough for anything; the well-advanced mirror was turned over upon it, fitting now very closely, and with the sweet morning air floating in from the pine-woods, and the birds singing all around, the monotonous task went on with its intermissions till Uncle Richard gave the final wash off, and said--"Breakfast!"

They were so far advanced now that Tom was as eager to recommence as his uncle, and by that evening so much progress had been made that the setting sun was made to shine in upon it, to be reflected back in a bright spot on the wall without the aid of water; while two evenings later, when the great round gla.s.s was stood all dry the polish upon it was limpid, and seemed to be as pure as could be. There was not the faintest scratch visible, and Tom cried in triumph--

"There, now it is done! Oh, uncle, it is grand!"

"Grand enough so far, my boy. We have succeeded almost beyond my expectations; but that is only the first stage."