So it was determined to make a canal from the Helder to Amsterdam. But the land was lower, almost all the way, than the sea. This rendered it impossible to construct the canal so as to make it of the same level with the sea, without building up the banks of it to an inconvenient height. Besides, it was just as well to make the canal lower than the sea, and then to build gates at each end of it, to prevent the sea water from coming in.
"Then how were the ships to get in?" asked Rollo, when Mr. George explained this to him.
"Why, there were two ways," replied Mr. George, "by which ships might get in. You see, although the canal is lower than the sea is generally, there is an hour or two every day when the tide goes down, in which the two are about on a level. Accordingly, by opening the gates when the tide is low, a communication would be made by which the vessels could sail in and out."
"But that would be inconvenient, I should think," said Rollo, "not to have the gates open but twice a day."
"Yes," said Mr. George; "and so, to enable them to admit ships at any time, they have built locks at each end."
"Like the locks in a common canal in America?" said Rollo.
"Yes," said Mr. George; "and by means of these locks, ships can be taken in and out at any time."
"I don't exactly understand how they do it," said Rollo.
"Let me explain it to you, then," replied Mr. George. "Listen attentively, and picture to your mind precisely what I describe, and see if you understand.
"First," continued Mr. George, "imagine that you are down by the sea shore, where the canal ends. The water in the sea is higher than it is in the canal, and there are two sets of gates, at a little distance from each other, near the mouth of the canal, which keep the water of the sea from flowing in."
"Yes," said Rollo, "I can picture that to my mind. But how far apart are the two sets of gates?"
"A little farther apart," said Mr. George, "than the length of the longest ship. Of course one pair of these locks is towards the sea, and the other towards the canal. I will call the first the sea gates, and the other the canal gates. The space between the two gates is called the lock."
"Yes," said Rollo, "I understand all that."
"Now," continued Mr. George, "a ship comes in, we will suppose, and is to be taken into the canal. First, the men open the sea gates. The sea can now flow into the lock, but it cannot get into the canal, because the canal gates are still shut."
"Yes," said Rollo.
"And, now you see," continued Mr. George, "that as the water in the lock is high, and on a level with the sea, the ship can sail into the lock."
"But it can't get down into the canal," said Rollo.
"No," replied Mr. George, "not yet. But now the men shut the sea gates, and thus shut the ship in. They then open the passages through the canal gates, and this lets the water out of the lock until it subsides to the level of that in the canal, and the ship settles down with it. But the sea cannot come in, for the sea gates, that are now behind the ship, are shut. When the water in the lock has gone down to the canal level, then they can open the gates, and the ship can sail along out of the lock into the canal.
"Thus they lock the ship down into the canal at one end, and when she has passed through the canal, they lock her up into the Y again at the other."
"Yes," said Rollo. "I understand it now. And shall we go into the canal through the locks in this way?"
"I don't know," said Mr. George. "I'll ask James."
So Mr. George beckoned to James to come to him, and asked him whether they should enter the canal through the lock.
"No," said James. "The ferry boat does not go into the canal at all. We go into a little dock or harbor by the side of it, and the passengers walk over the dike, and down to the canal, where they find the boats ready for them that they are to take."
"Why don't they pass from those boats through the locks, and let them come across to Amsterdam?" asked Rollo, "and then we might get on board them there, and so not have to change from one boat to the other."
"Because it takes some time, and some trouble," said James, "to pass any thing through the locks, and it is not worth while to do it, except in case of large and valuable ships. So the boats and steamers that ply along the canal are left inside the lock, and the passengers are taken to and from them by the ferry boat."
The ferry boat, by this time, began to approach the shore. It entered into a little opening in the land, which formed a sort of harbor. Here the passengers were landed at a wharf, which was surrounded by small buildings. Thence they ascended what was evidently a large dike. When they reached the top of the dike they saw below them, on the other side of it, the beginning of the canal. It lay several feet lower than the water of the harbor in which they had left the ferry boat; but it was quite wide, and it was bordered by broad dikes with avenues of trees upon them, on either side. On one side, under the trees, was a tow path, and on the other a broad and smoothly gravelled road.
Two boats were lying moored to the wharves at the side of the canal. One was a long, sharp, and narrow steamer, which was going through the whole length of the canal to the Helder. The other was a trekschuyt, or canal boat, which was going only a short way, to the nearest village.
The passengers that came in the ferry boat divided into two parties, as they came down the dike. One party went to the steamer, the other to the trekschuyt. Mr. George and Rollo, of course, went with the last.
The trekschuyt was a curious sort of boat. It was built like the Noah's ark made for children to play with; that is, it was a broad boat, with a house in it. The roof of the house, which formed the deck of the boat, was flat, and there were seats along the sides of it, and a railing behind them on the margin, to keep people from falling off. At each end of the house were two flights of steps, leading up to the roof or deck, and below them another flight, which led down to the little cabins below.
As soon as Rollo got on board, he first ran up on the deck. He sat down on the seat upon one side, and then, after looking about a moment, he ran over to the other side, and sat down there. Then he got up, and said that he was going below to look at the cabins.
Mr. George, all the time, stood quietly on the deck, looking at the canal, and at the country around. He could see the canal extending, in a winding direction, across the country; but the view of it was soon lost, as the winding of its course brought the dikes on the sides of it in the way so that they concealed the water. He could, however, trace its course for some distance, by the masts and sails of vessels which he saw at different distances rising among the green trees. Along the dike, on one side, was a high road, and on the other, a tow path. Different boats were coming and going in the part of the canal that was near. They were drawn by long and slender lines, that were fastened to a tall mast set up near the bows of the boat. Some were drawn by men, and some by horses.
[Illustration: THE TREKSCHUYT.]
Before the trekschuyt had gone far, after it commenced its voyage, a great ship was seen coming on the canal. She was coming from the Helder. It was a ship that had come from the West Indies, and was going to Amsterdam. The wind was contrary for her, and they could not use their sails, and so they were drawing her along by horses. There were two teams of horses, eight in each team. The view of these teams, walking along the tow path, with the immense ship following them in the canal, presented a very imposing spectacle.
The trekschuyt started before the Helder steamer; but it had not gone far before Rollo, who had now ascended to the deck again, saw her coming up behind very rapidly.
"I tell you what it is, uncle George," said he, "I wish you and I were on board that steamer, and were going along the whole length of the canal."
"So do I," said Mr. George.