Part 31 (2/2)

”Then it must be something like surveying?”

”Yes; the same principles are applied. Here is a sketch, which shows the earth A, and B is the equatorial line. C is the position of the sun on September 20, or on June 20.”

”Why are they in the same position on both days?”

”Yes; the sun crosses the equator September 20, on its way south, and then it again recrosses the equator coming north six months afterwards.

On either of those days, if a person should stand at D, and look at the sun, there would be a line E, which projects out from the earth to the sun, and that is called the equatorial line.”

”It is exactly at right angles to F, which pa.s.ses through the poles. Now the drawing shows two other positions, namely G and H. These represent the extreme points of the travel of the sun north and south, or the positions that the sun occupy on Dec. 20, and June 20 of each year.”

”I see,” said Harry. ”The points G and H are just 23 degrees north and south of the equator.”

”That is correct, and there is another thing which can be learned from their positions.”

”I know what it is.”

”What?”

”It gives another line, or angle.”

”So now we have two angles, this, and the equatorial line. Then, we know the exact distance of the sun from the earth, and this gives the first measurement, and with the angle formed by the line I, taken in connection with the line E, it is easy to determine just where, or how far the sun is to the north or to the south, and if you did not, for instance, know the time of the year, a man could by such a measurement, tell, by the angle thus formed, the exact date.”

”I understand that now,” remarked George. ”The sailor, in getting the angle, simply measures that, and if he knows where the sun is on that day he will then have two angles, one that he knows beforehand, and the other that he finds out by looking at the sun.”

”That is correct. The Nautical Chart gives all that information, so that it saves a large amount of work in making the calculations.”

”That gives the way to determine positions north and south. But how about east and west?”

”In the same manner exactly so far as the angle measurements are concerned, but in this case, instead of taking the time, in days or in months, as in reckoning north and south, we must take time in minutes, and to do that the entire globe is laid off in minutes and degrees, which the nautical tables give, and the mariner knows when he obtains a certain angle just how far east or west he is located by the chart.”

”But if he has no chart?”

”Then he must figure out the position for himself, which he can do if he has what is called Greenwich, or standard time, and has, also the correct time of the day where his s.h.i.+p is.”

Land was beyond; there was no question of that. It rose out of the water higher than the island they had just left, which the boys had named _Venture_ Island.

The Chief knew nothing of the land before them. He had told John that years before he learned that there was a land where there were many bad people, who killed and ate each other, but he did not know the exact direction.

The vessel was sailed along the coast, and the field gla.s.ses were used to scan the land. It had the appearance of the other islands which they now knew. Vegetation was magnificent, and growing everywhere, but there was not the sign of a habitation anywhere.

After an hour's sail they rounded a point, and beyond was the first cove, or indentation along the coast. To that John directed the course of the vessel, and they ran in very close, since he knew from the abrupt sloping beach that it must be a deep bay.

The men could scarcely man the boat quickly enough. A dozen of them, together with John, Muro and Uraso, took the first boat, while a second boat was filled with the warriors who also were accompanied by some of the natives of Venture island.

The Professor and the others remained on board, while the party made the preliminary examinations of the immediate neighborhood. John formed two parties, one under command of Muro, and the other of Uraso. The boys were with Uraso, while he was with Muro. The object was to find out as quickly as possible what they would have to meet, and the result would enable them to determine the future plans.

”It is understood, now,” remarked John, ”that the two exploring parties shall take the two courses outlined, Muro and his men, to go directly east, while Uraso will take a course to the northeast, and proceed in that direction for three hours, and then the two parties are to turn toward each other, and mutually report. This will give us an opportunity to find out something, unless the island is a very large one, and requires subsequent exploration to ascertain whether it is inhabited.”

<script>