"What is the matter? Are you worried?"

"No, but I am trying to remember where I have heard that name before. But so much has happened to-day that I can't recall it."

It had been indeed, a full day since the Bobbsey twins had left their home in Lakeport that morning, and Mrs. Bobbsey insisted on Flossie and Freddie, at least, going to bed early. This the small twins were glad enough to do, after they had told Nan and Bert the different things that had happened after they got on the express train.

"It was an awful splendid store," said Flossie, in speaking about Mr.

Whipple's establishment.

"Bigger'n any store in Lakeport," added her twin.

"And the nicest clerks that ever was," went on Flossie. "Why, one of 'em had a whole counter full of cologne, and she squirted some on me when I went past, and it smelled awful good!"

After breakfast the next morning, when Mr. Bobbsey had finished sending some telegrams and telephone messages, he asked the children what they first wanted to see in New York.

"The monkeys!" cried Flossie and Freddie.

"I want to go on Fifth avenue and see the lovely shops and stores," said Nan.

"And I want to go to the history museum and see the stuffed animals and the model of a whale," said Bert, who had been reading of this.

"Well, how would you like to go and see some live fish?" asked Mr.

Bobbsey. "That ought to satisfy all of you, and Nan can see some stores on the way to the Aquarium. I have to go downtown in New York," he said to his wife, "and I can take the children to the Aquarium at the Battery as well as not."

"All right," said Mrs. Bobbsey. "If you'll do that I'll stay here and rest. Afternoon will do for me to go out. Now mind, Flossie and Freddie, don't get lost again!"

The small twins promised they would not and soon all four were on their way downtown with their father. This time they went in the subway, or underground road, which, as Freddie said, was like one big, long tunnel.

"We'll get out at the Brooklyn Bridge or City Hall Park," said Mr.

Bobbsey. "I have to see a man in the City Hall, and from there we can walk to the Battery, as it is a nice day. Or we can ride, if you get too tired."

The children were sure they would not get too tired, and a little later they all got out at the subway station at Brooklyn Bridge.

There were many persons hurrying to and fro, trains coming in and going out, and lights all over, making the children think it was night, though it was in the morning.

"Wait here just a minute," said Mr. Bobbsey, showing the twins a less crowded place where they could stay. "I want to get a magazine over at the news-stand," he added.

The magazine he wanted had been put away under a pile of papers, and as the boy was getting it out Flossie caught sight, down the platform, of a man pasting up on the advertising boards in the underground station, some new posters.

"Oh, maybe it's signs about a circus, Freddie!" cried the little girl "Come on and watch!"

Freddie was always ready to go, and he had darted off after his sister down the long platform before Bert and Nan saw them. When the two older children missed the younger twins they looked hurriedly about for them.

"There they are--watching that bill-poster," said Bert. For the underground subway stations are much used by advertisers, gaily colored sheets of paper being pasted on boards put there for that purpose.

"You mustn't run away like that!" said Nan to Flossie, as she came up to her sister, to lead her back.

"We wanted to see if it was a circus poster, but it isn't," returned Freddie.

"Well, come on back. Daddy will miss us," declared Bert. He started back--at least he thought he did--for the place where their father had told them to wait for him. But the subway station under the New York sidewalks was so large and rambling, there were so many stairways leading here and there, up and down, and there were so many platforms that it is no wonder Bert went astray.

"Where are you going?" asked Nan at last.

"Well, I was trying to find the place father told us to wait," Bert answered.

"It's over this way," said Nan, pointing just the other direction from the one in which Bert was walking.

"All right, we'll try that, but it seems wrong," he stated.

They walked a little way in that direction. They saw nothing of their father, however, and there were fewer people on the platform where they now were.

"Oh, dear!" cried Flossie, "I'm thirsty! I want a drink!"

"So do I!" added Freddie.

Nan and Bert looked about them. They were still in the underground station, and they could see trains coming in and going out, and crowds of people hurrying to and fro. But they could not see their father nor the place where he had told them to wait. At last Nan said:

"Bert, I don't know where we are! We're lost!"

CHAPTER XI

FREDDIE AND THE TURTLE

Bert Bobbsey looked all around the big underground subway station before he answered Nan. Then he took off his cap to scratch his head, as he often did while thinking. Next he looked down at Flossie and Freddie.

If he thought he was going to find the two little twins in a fright at what Nan had said about being lost, Bert was mistaken. The two flaxen-haired tots were looking down the long platform, into the gloom of the long tunnel of the subway.

"Aren't they funny, Freddie?" asked Flossie.

"Yep, awfully funny," was Freddie's answer.

"What's funny?" asked Bert, wishing he could see something at which to laugh.

"Those red and green lights down the track," explained Freddie. "They blink so funny and come up and go out----"

"Just like winking at you," said Flossie. "I like it down here. It isn't like the dark tunnels we went in on the steam cars."

"Well, I'm glad _somebody_ likes it," said Bert to Nan. "But say, how do we get out of here?"

"I'm sure I don't know," she said. "When I ran after Flossie I didn't look which way I was going."

"I didn't, either. Queer how we could get lost in a place like this," and Bert seemed worried and spoke more loudly than he intended. Freddie heard what his brother said and looked up quickly.

"Are we _really_ lost?" he asked.

"It seems so," answered Nan. "I ran after you two, and we have walked about so many platforms and up and down so many stairs that I can't see or remember the place where Father told us to wait for him."