Those were the names of the four children.  Bert and Nan were the older twins, and Flossie and Freddie the younger.  You are first told about them in the book called “The Bobbsey Twins,” and in that you learn that the Bobbsey family, consisting of Mr. and Mrs. Richard Bobbsey and their four children, lived in Lakeport, an eastern city on the shore of Lake Metoka, where Mr. Bobbsey had a lumber business.

In the family, though not exactly members of it, were Dinah, the jolly, fat, colored cook, and Sam Johnson, her husband.  Then we must not forget Snap, the dog, and Snoop, the big cat.

Following the first book are a number of volumes telling of the adventures of the Bobbsey twins.  They went to the country to visit Uncle Daniel, and at the seashore they had fun at the home of Uncle William.  After that the Bobbseys enjoyed a trip in a houseboat, they journeyed to a great city, camped on Blueberry Island, saw the sights of Washington and even sailed to sea.

As if this was not enough Mr. and Mrs. Bobbsey took their children on a western trip among the cowboys, and just before the present story opens Bert and Nan, with Flossie and Freddie, had come back from Cedar Camp, where they had had some exciting adventures.

Now it was summer again, and one of the first delights of that season was the Sunday school picnic which had started off so well but which seemed likely now to end in an accident.

It was too bad that one truck should have gotten safely over the bridge, and that the other had to break through.  The second truck was heavier than the first.  The first may have cracked the bridge beams and the second one broken them.

“Careful now, children, careful!” warned Mr. Blake.  “Don’t jump down!  Come to the end of the truck and I’ll lift you down!”

“And as soon as you are down walk to the other side of the bridge; don’t run—­walk!” ordered the driver.

Bert remembered that it said this on the programs of the moving picture theaters, and he decided it was good advice.

One by one the children made their way up the sloping floor of the truck to the tailboard, and there Mr. Blake, Mrs. Simpson, and other men and women helped the little ones down.

“Oh, I feel like fainting!” sighed Grace.

“Don’t be silly!” exclaimed Nan.  “Nothing is going to happen!”

It was a good thing Nan felt this way, though, as a matter of fact, something dreadful might happen at any moment.  If the cracked beams of the bridge should break all the way through, the auto would slide down into the water.  And, though the creek was not very deep, still many would be hurt in the crash.

The Bobbsey twins, being nearest the rear of the auto, were among the first off.  They did what the driver told them—­walked quietly off the bridge.

At the farther end they joined the picnic party that had gotten off the first truck.  And there, almost breathless, they watched the work of rescue going on.