“Well, Mary,” said he, “have you come to make the oscillations?”
“Yes,” said Mary. “I have brought some thread for strings, and I want you to get some pebble stones—some large, and some small ones.”
Rollo went for the pebble stones, while Mary looked about for a suitable place for making the experiments. In a corner of the yard there was a bench under a tree, and the branches came down pretty low. Mary thought that this would be a good place, for she could tie her strings to these branches with the pebbles hanging down below; and she and Rollo could watch the oscillations, while seated upon the bench.
Mary took her station here, and Rollo presently appeared, with the crown of his cap half filled with pebble stones. Mary said they would do finely. She poured them out upon the bench by her side, and Rollo put his cap upon his head again.
“Now, Rollo,” said she, “we will study the art of experimenting.”
“No,” said Rollo, “we are going to study oscillation.”
“Yes,” replied Mary; “the experiments are to be on oscillations; but what I want principally to teach you, is, the proper way to make experiments.”
“Well,” said Rollo.
Mary said no more, but she proceeded to tie a small pebble to the end of one of the long threads which she had brought out with her. Then she tied the other end of the thread to the branch of the tree, which was over her head. The pebble then hung down before them, so that both Rollo and herself could plainly see all its motions.