In a brief time both boys returned. "George says he did not hear the shots from the river."

"They were as plain as your own."

George did not know how to explain it. The Professor moved forward. "Let us get out into the opening."

As they reached the clearing beyond the wood, and the Professor saw the steep bluffs beyond, he laughed, and looking at the hills, said:

"That is where the shots came from."

His amusing smile was rea.s.suring, although his words were not.

"That bluff over there is about 2,000 feet from here. We had better find out what he is doing there."

"Two thousand feet; and somebody there!"

"I did not say somebody was there, but that the noise of the shot came from that place."

"Do you think it was simply an echo?"

"Undoubtedly; didn't you hear Baby's cries repeated?"

"But how do you know that the hills are 2,000 feet away?"

"Sound travels at the rate of 1,040 feet per second, and I made a mental calculation that it took four seconds for Baby's cries to come back from the hills. In that case the sound had to go to the hills and back again, and it would, therefore, take two seconds to travel one way. Do you understand?"

"Oh, yes; that is perfectly clear."

The land now became more rolling, and was occasionally broken by ravines; and sometimes they had difficulty in getting their yaks and wagon across and over the rough ground.

Fallen trees were numerous; there were little mounds here and there, made by the remains of uprooted trees, which had long ago decayed, all of which made their traveling laborious and slow.

Here wild animals became more abundant, and wild game was found on every side. Several good shots by the boys replenished their larder with bird meat.

"See that bear!" cried Harry in great excitement.

The boys, as well as the Professor, were out with their guns at once.

"Follow him up quickly now," and the Professor could hardly keep pace with them. The bear did not seem to be greatly frightened, and when Harry, who was ahead, stopped and aimed his gun for a shot, he was less than a hundred feet away. The shots from the two boys came close together, and bruin stopped in surprise, then, with a snarl, turned around and in a lumbering, shuffling movement started for the boys.

If either shot had taken effect it was not noticeable. The boys turned to run, one going to the right and the other to the left. This did not seem to disconcert him in the least, as he went right on. He had seen the Professor, who stopped and sprang to one side and bringing up his gun awaited the charge of the bear.

The boys, encouraged by the tactics of the bear in avoiding them, turned again, because they now appreciated that the Professor was in the bear's path.

"Don't shoot, boys; let him come nearer."

When he came within fifteen feet the Professor fired, and the boys also shot. The bear reared up, gave a terrific growl and again shambled forward, this time making a beeline for the wagon. This was too much for the yaks; they turned, almost upsetting the wagon, and Baby commenced to shriek in the most approved fashion.

[Ill.u.s.tration: _Fig 3. THE BEAR_]

Neither George nor Harry could wait any longer. They followed and rushed past the Professor, who now had the only loaded gun.

"Take this, Harry; your guns are not loaded."

Harry turned and grasped it and without stopping went in pursuit. Before he had reached the former location of the wagon the animal ran into a tree, which threw him back on his haunches, and after several efforts to raise himself, fell over on his side.

The Professor's shot had entered his left eye, but the vitality of the animal was such that he ran nearly a hundred feet before it took effect.

The yaks were soon rounded up. It is a wonder that more damage was not done. Aside from the displacement of their bedding, and the ditching of some of the cooking utensils, everything was found intact.

"That was a rather ill-advised adventure on our part. We should have guarded our supplies; but I was as much to blame as you were. We must be more careful in the future."

On every side the rough character of the land was more apparent, and it was becoming more and more difficult to find tracks which were suitable for the team.

"This matter of going further with our wagon is now getting to be a serious problem. I think we should turn to the right and move in the direction of home, or direct our course southeast toward the mountains on the other side of South River."

"I think we have discovered enough on this trip," was Harry's conclusion.

George a.s.sented, so that on the twelfth day of their journey the yaks were directed towards home. For two days the travel was southeasterly, through the most broken and tortuous paths, crossing innumerable small streams and rivulets on their course. During this troublesome part of their journey the weather was stormy, with numerous rains, some of them so prolonged as to prevent traveling for hours, so that they made less than twenty miles during that time.

[Ill.u.s.tration: _Fig. 4. DIAGRAM OF THEIR TRIP_]

On the third day, however, the ground became more level and less broken, the sun appeared, and they felt happy at the thought of getting back again.

Thus far in their wanderings they had kept their reckonings, as well as they could without instruments, and that evening the chart was again consulted, as usual. The drawing (Figure 4) shows how it looked with the course of their journey.

When they started from the Cataract home at nine o'clock in the morning, they made an observation of the sun, using a vertical pole so as to get the exact direction of the falling shadow. A distant object was then selected, a prominent tree, as far off as possible. The Professor had prepared an adjustable bevel square, which was simply two legs hinged together at one end, by means of a set screw, like a compa.s.s.

[Ill.u.s.tration: _Fig. 5. BEVEL SQUARE_]

"Now, boys, I want to show you how we can make a fairly good chart simply by the use of this adjustable square, and this will also be of service to us in measuring heights of objects, as well as directing our course. It is now nine o'clock, and you will see that our pole (A) throws a shadow to the southwest. Supposing now, we direct the first leg of our journey to that large tree (C), to the west of us. If, now, we put one leg (D) of our rule along the shadow line, and the other leg (E) along the sight of the line (F), which goes to the tree, we shall find that the distance across between the ends of the bevel square is just two feet. It happens in this case that the tree (C) is due west from our observation point; so we have at nine o'clock each morning a means whereby we can always determine the true east and west."

"But supposing we lose our reckoning during the day, on account of cloudy weather, or by going through the forest, where we cannot make observations?"

[Ill.u.s.tration: _Fig. 6. SIGHTING THE DIRECTION_]

"We could, probably, travel an entire day in one general direction, without being more than a few miles out of our course, north or south, and our direction immediately made out the next day."

"Wouldn't it be a good idea to prepare angles at different times of the day, in the forenoon and in the afternoon?"

"That is the proper thing to do, so as to enable you to make observations from the angles at all times. A chart could then be made from that which would show at a glance what the value of each angle is."

"We shall certainly have to do that; but what interests me as much is, to know how far we have traveled. Can we also tell that by the sun?"

"Yes; but to do so will depend on the accuracy of the observation. For the present, with only a single instrument, the bevel square, we must be content to make our calculations exactly at midday, when the shadow points due south. Or, in the northern hemisphere, when the shadow points due north. I want you, in the meantime, to think over that problem, as it is a very interesting one, and we will take it up when we are not so tired."

CHAPTER IV