“The length of the string,” replied Mary.
“O yes,” said Rollo, “it may depend upon that.”
“Let us see,” continued Mary. “There are three experiments we have already proposed; a large and a small pebble; a pebble and a cork; a long and a short string; and now there is one more,—a long and short arc.”
“How?” said Rollo.
“Why, if I draw up the weight, which forms the pendulum, pretty high, it will swing back and forth through a long arc. But if I move it only a little way, it will swing through only a short arc, and that may make a difference in the length of the vibrations.”
“Well,” said Rollo, “and now let us try.”
“First, let us see whether we have got all the apparatus we want. Here are strings and pebbles,—only we want a cork.”
“I’ll go and get one,” said Rollo.
So Rollo went off towards the house to get the cork. In a few minutes he came back, saying,
“I have got the cork. Now how shall we begin?”