THE DISTANT SHIP AND ITS DISAPPEARANCE

"What is that weed you have, Professor? The root looks like a parsnip."

"It may be something we can drink."

"It looks just like a weed that grows all over our farm at home."

"I have no doubt of it. This is the endive, as it is known in the States, but it is really chicory."

"I have heard of chicory; isn't it used as a subst.i.tute for coffee?"

"Princ.i.p.ally on account of the bitterness in it. The French make the greatest use of it, because they claim it gives strength to coffee."

"What part of it is used?"

"The root; the bulb you see here, and they have a curious way of preparing it. The root is dug up before the plant shoots into flower, and is washed, sliced and dried! it is then roasted until it is of a chocolate color. Two pounds of lard are roasted with each hundredweight; and afterwards, when ground and exposed to the air, it becomes moist and clammy, increases in weight, and smells like licorice. When put into cold water it gives a sweetish bitter taste, not unlike coffee."

"Let me try some of it, and don't say anything about it to Harry. And now, while I think about it, why couldn't we make some crocks out of our clay, so we can use them for our milk. We can't put them in the copper vessels and the iron is just as bad."

"That is a splendid idea; and you might as well vitrify them."

"What do you mean by vitrifying them?"

"Putting the glaze on them, just like the common crocks have."

"That would be simply fine."

The Professor explained the process, which consisted in making the crocks out of the best clay available, and then burning them. Afterwards an intense heat must be made in the furnace, and after soaking the crocks in a strong solution of salt brine, they must be put in and burned again; the greater the heat, the better.

The boys started at this with a will, and when they had arranged to make the crocks they found it most difficult to put them into a round and uniform shape.

"I would suggest that you make a potter's wheel for that purpose."

"A potter's wheel? What is it like?"

"It is the simplest thing imaginable. Do you think, Harry, you could turn out a wooden vessel just the size of the outside of an ordinary milk crock, and turn it with a central stem below, and also have a little pulley on that stem?"

The Professor made a drawing (Fig. 29), which shows just how he wanted it made. In the drawing, A is the cup-shape, which is the size and shape of outside the crock; B is the central stem; and D is the small pulley on the stem. This was mounted in a pair of arms like CC, and a belt was attached to the pulley.

"You have made a very creditable article. Now you may make a flat paddle, and shape one end so that it will be just like the inside of the crock."

[Ill.u.s.tration: _Fig. 29. Potters Wheel._]

The drawing (Fig. 30) shows how it was made, with a cross handle at the upper end.

That day the crocks were turned out in the following manner: The potter's wheel was rotated about sixty turns a minute, and the clay, in a plastic state, was put in the cup-shaped top, and the hands used to force the clay up the side wall. When the crock was formed in as even a manner as it could be by hand, the blade described was used to make the interior uniform.

The potter's wheel is one of the oldest tools known. Its use can be traced back for more than four thousand years, when it was well known by the Egyptians.

[Ill.u.s.tration: _Fig. 30. Forming blade for inside of Crock._]

Since the day that the boys visited Observation Hill, at the time they discovered the skeleton and fragments of the boat, no attempt had been made to visit the cave. That was the mission when they accidentally made their surprising discovery.

George did not, however, feel that they should again make the attempt until they had a better lighting means than the unsatisfactory candles, and when the supposed petroleum vein dashed all hopes of lighting material from that quarter, the only remedy seemed to be by way of improving their candle-light.

Harry had progressed well in the making of the battery. It was now in a completed state, and he announced that the first tests would be made the next day. In the morning all a.s.sembled in the factory, and the sulphuric acid solution was made up.

The Professor inspected the batteries. Ten cells had been prepared, so that they could have, at least, fifteen volts. When all the cells had been connected together--that is, the positive pole of one cell with the negative pole of the other--a wire was attached at each end of the row of cells, at the last electrodes, so as to form the outside connections.

When the two outside wires were brought together and their contact broken a spark was plainly shown, which was an indication that the battery was generating electricity. The boys danced about with joy at this exhibition. From that time forward the battery was one of the most interesting things in the laboratory, and what they finally accomplished with it will be fully detailed as we go along in their history.

George thought he saw a way to make the light necessary for the cave.

"Why can't we rig up an electric light now and explore the cave?"

"We might do that, but we have several things to do before we can have light from that source."

"Haven't we the electricity for it?"

"Do you know how many years electricity was known before electric light was discovered? Before we can utilize this agency for lighting purposes, we must make a machine which will produce a vacuum; we must make gla.s.s; we must learn to carbonize threads; and the art of blowing gla.s.s would be a necessary accomplishment."

"As usual," said Harry, "something must be made to make something that makes something else."

"But can we make electric light without putting it in a gla.s.s bulb?"

"Yes; we can make what is called the arc light; instead of the incandescent."

"What is the difference between the two?"

"In the incandescent, such as we talked about making, a thin carbon filament is enclosed in a gla.s.s bulb, from which as much air as possible has been exhausted, and when a current of electricity pa.s.ses through this filament, it is heated up to a white heat."

[Ill.u.s.tration: _Fig. 31. The Electric Arc._]

"Why doesn't it burn out?"

"It does burn out in time. What preserves it, however, for a long time, is that most of the oxygen has been exhausted from the bulb----"

"Oh, yes; I know, there must be oxygen to support combustion, so that the carbon is merely heated up?"

"I am glad you remembered that. The arc light, on the other hand, depends on an entirely different thing. You have seen, no doubt, the long black pencils used in the large lamps. That is carbon also, made out of ground c.o.ke, molded and compressed into shape."

"What does arc mean!"

"Did you notice that when we put together the two circuiting ends of the wires in our battery this morning, we could not notice the existence of a current, but whenever we pulled them apart we had a spark?

"Let us now make a little experiment which will show you the arc. You see, I am making a sharp point at the end of each wire, and I will fasten one of the wires so it cannot be moved. Now the other wire will be placed with its point as close to the other points as possible, and so fixed to the support that we can adjust it still closer and hold it.

See, the points now touch each other. I will move one of the wires the slightest distance away from the other. There! see the light?"