While the work of getting out the planking for the boat was going on, and the plowing had now been resumed, since the new yoke of oxen were fitted to do the work, the boys were not forgetful of the usual weekly outing. They had several quite important things right at home which needed looking into, if they wanted to solve some of the things on the island. First, the cave, which they had twice attempted to explore; the search for their lost boat, which had the strange rope and oars; and the mystery of the flag and pole.
These things weighed heavily on their minds, because these happenings were close at hand. But what made the greatest impression on the minds of all was the finding of the _Investigator"s_ lifeboat. It seemed almost like a call to them from the interior. The impatience of the boys was almost beyond restraint, at times.
"It does seem to me that we should not delay an hour in making some effort to explore the direction the boat came from," was George"s view of the situation as they canva.s.sed the subject.
"That is my idea, also, and I am not in favor of giving much more time to hunting or other forms of recreation until we know how that boat came to South River."
"Yes; I can appreciate how anxious you are," said the Professor, after the boys had given their views. "What we are doing, however, is essential from every point of view. We must prepare provisions, so that we shall be able to know where we can get them in case of need. On the other hand, weapons are necessary, which take time to construct. If, however, it is thought advisable, we might make a trip of explorations along the South River, beyond the falls, the time to be limited to a week; but I have my doubts of the wisdom of such a course."
This suggestion appealed strongly to the boys, who were always keen for anything which savored of adventure, and it was some time before the boys could reconcile themselves to the saner and more business-like course of completing the boat and making the trip by water.
The weather was beautiful, and vegetation was springing up in abundant profusion everywhere. Magnificent showers fell at intervals, and the rainbows, more beautiful than any they had ever heretofore seen, spanned the heavens after the showers.
This had been noticed during the previous year, but now, after nine months of their life, with the wonderful insight which their needs had instilled into them, made them very observant of every phenomenon.
"I have often wondered," observed George, as he gazed at the beautiful broad band which formed a crescent across the heavens, "why there are never any rainbows in the middle of the day. They are never seen except in the morning or in the evening, and usually only in the evening."
"In order to understand that it will be necessary to explain what a rainbow is. As I stated previously, light is merely vibration. Now colors are formed by the different lengths of the vibrations, just the same as the different musical notes are made by the different vibratory lengths. To understand this more fully, I make a sketch (Fig. 7), which shows just what I mean. You will see that red is the lowest musical pitch, which we will call C, and to the right is a long, wavy line. D, the next pitch higher, might resemble orange, with the wavy line a little shorter, and so on, until we reach the highest note in the scale, where the wave lengths are very short. You have probably noticed that a drop of water in the sunshine glistens, and, if closely observed, may have seen that it was colored, particularly blue or green. As the rays of the sun strike the globe of water, they produce different wave lengths, and in that way make it appear to you as being possessed of colors. Now, a rainbow is nothing more nor less than sunlight pa.s.sing through the drops of water which are suspended in the air and causing a refraction of the light. At noon the sun shines down from overhead, and we are not in the proper position to see this refracted light; but in the morning or in the evening the sun shines against the earth at an angle. At those times we are able to see the effect of refraction by the colors produced.
[Ill.u.s.tration: _Fig. 7. THE COLOR SPECTRUM_]
[Ill.u.s.tration: _Fig. 8. REFLECTION ANGLE_]
"When you throw a ball against a wall at an angle, it bounds away at the same angle. That is reflection, and is just exactly what light does when a ray strikes a mirror. If, on the other hand, the gla.s.s had no mercury on it to reflect the light, the ray would not go straight through, but would bend, just as you have seen a stick in a gla.s.s of water appearing as though it was bent below the water line. That is refraction."
Two weeks of very vigorous work had now been put in since the yaks had disappeared, and the wagon was still at the edge of the forest. George was anxious to recover it, with the new team, and with Harry started out early in the morning to make up as much as possible lost time, as every hour was considered valuable in their enterprises.
The yaks could be ridden as well as horses, but the greater part of the way were driven. One of the guns which had been completed was taken along, as well as the only pistol which the Professor had saved. In less than three hours the forest was reached and they were soon within sight of the wagon.
"What have we there?" cried Harry, as they neared the spot.
"Our yaks! And where do you suppose they have been?"
Close by the wagon were the yaks, as though patiently waiting for the boys. They made no resistance, nor show of fright, when the boys approached. One of them, Jack, still had the strap tied to the horns, and it was the halter which had been attached to the tree at South River.
A hasty examination was made, but if either of the boys came to any conclusion concerning it, nothing was said. Without wasting time, the team brought with them was yoked up and the broken wheel replaced by a new one. The repairs to the wagon tongue did not take long, and they were ready for the return.
"What shall we do with Jack and Jill?" Those were the names bestowed on the first team. "Let us see if they will follow us."
They had gone fully one hundred feet before the yaks made any sign, and then slowly followed, thus a.s.suring them that no care or attention would be required in that direction. Both boys were intensely delighted at the recovery of their favorites and could not get home fast enough to give the Professor the good news.
Nearing home, the Professor, who was on the watch, came out to meet them, waving his hat at the sight of Jack and Jill. When the latter came up he went over and affectionately petted the creatures, who seemed to realize the welcome.
"I hope they are as glad as we are; I can understand why they got away; look at the end of this thong." It plainly showed the teeth of some animal which had gnawed the leather of which it was made.
"So you have been out prospecting, too?" was Harry"s query, as he saw the queer-looking reeds on the table in the laboratory that evening.
"What do you call that?"
"Our honey has been getting low, and I took the occasion to-day to bring in some samples of sugar."
"Is that sugar cane?"
"Yes; the true sugar cane."
"Is that different from sorghum?"
"This is the species which grows in the southern part of the United States. The kind you know and which is cultivated in the Northern States, is the Chinese Sorgo, or, as we call it, sorghum. It is equal in quality and in quant.i.ty to the southern species and is readily treated to produce mola.s.ses or sugar."
"What is that peculiar flower, if it is a flower? I never saw a flower like that; it seems to be hard."
"I was surprised to find this. It is called the Tamarisk. This long, oval-shaped part is made by an insect which inhabits the plant, and is eaten by the inhabitants in the plains east of the Mediterranean Sea. It is there called Mount Sinai Manna, and is supposed to be the Manna which the Jews found when they were in the Wilderness after the Exodus."
"I think we have properly named this place Wonder Island."
In the volume preceding this, when they first considered the building of a new boat, it was decided to graft an extension to the after part of their wrecked lifeboat; but when the second one was found, and calculations were made as to its usefulness, it was discovered that such a course would not be wise; hence the larger vessel was found to be the only solution.
The newly discovered boat was, however, a valuable addition, as it afforded a means by which short trips could be made, and Harry quietly set to work making a sail and rigging up a mast, so that the long-cherished desire to make these trips could be undertaken before they were ready to launch the real vessel. It was hauled up on sh.o.r.e and caulked and new parts added to make it adaptable for the purpose.
While engaged at this work he removed the cross seat which still remained, and in doing so was surprised to find a piece of cardboard which had been hidden, apparently, at the end of the board. Eagerly picking it up, he saw writing on it, with the following words: "We cannot hold out much longer. Wright and Walters were captured yesterday.
WILL."
[Ill.u.s.tration: _Fig. 9. THE HIDDEN MESSAGE_]
Harry could hardly contain himself, as he rushed up to the laboratory, crying out: "George, come here, quickly! I have found something!"
Without waiting to see whether George heard, he rushed into the Professor"s den with the paper in his outstretched hand. "Look at this; don"t you remember Will Sayers? I am sure it is Will."
George heard his excited voice, and appeared without any delay.
"What is it now?"
The Professor was reading the sc.r.a.p, and silently handed it to George.
"Did you know either of the boys mentioned in this?"
Neither had any recollection of Wright or Walters, but they inferred that the writer must be Will Sayers, one of the companions. The Professor had no recollection of the boy, nor could he remember the other names.
"Let us examine every part of the boat," was the Professor"s first suggestion. "We may find something more to give some clue."
The boys rushed down to the beach where the boat was moored, the Professor following.
"Show us the exact location of this strip."
"I had just taken off this cross seat, and as I did so this piece fell from the end."
"Let us put it back again and see how it fits into that place."
When it was replaced they noticed that a crack was left at each end of the seat, not exceeding an eighth of an inch.
"It is very plain that the piece you found was at this end, and if it was folded as this crease indicates, it could have been concealed there and thus escaped our observation." After some minutes" examination, he continued: "This piece must have been there for some time."