thinking of what made it fall."

"Why, I could have told him that," said Lucy; "because the stem snapped
and there was nothing to support it."

"And what then?" asked her father.

"Why, then, of course it must fall."

"Ah!" said her father, "that is the point: why must it fall?"

"I am sure I don't know," said Lucy. "I presume it was because there was
nothing to keep it up."

"Well, Lucy, suppose there was not--does it follow that it must come to
the ground?"

"Yes, certainly," replied Lucy, wonderingly.

"Let us see," said her father; "but first answer this question: What is
an animate object?"

"Any thing that has animal life, and power to move at will," replied
Lucy.

"Very good," said her father; "now, what is an inanimate object?"

"Any thing that does not possess animal life, or can not move at will."

"Very good again," said her father. "Now an apple is, of course, an
inanimate object; and therefore it could not move itself, and Sir Isaac
Newton thought that he would try to find out what power moved it."

"Well, then," said Lucy; "did he find that the apple fell, because it
was forced to fall?"

"Yes," replied her father; "he found that there was some force outside
of the apple itself that acted upon it, otherwise it would have remained
forever where it was, no matter if it were detached from the tree."

"Would it, indeed?" asked Lucy.

"Yes, without doubt," replied her father, "for there are only two ways
in which it could be moved--by its own power of motion, or the power of
something else moving it. Now the first power, you know it does not
have; so the cause of its motion must be the second."

"But every thing falls to the ground as well as an apple, when there is
nothing to keep it up," said Lucy.

"True. There must therefore be some power or force which causes things
to fall," said her father.

"And what is it?" asked Lucy.

"If things away from the earth can not move themselves to it," said her
father, "there can be no other cause of their falling than that the
earth pulls them."

"But," said Lucy, "the earth is no more animate than they are; so how
can it pull?"

"That is not an ordinary question, but I will try an explanation," said
her father. "Sir Isaac Newton discovered that there was a law in nature
called attraction, and that all bodies exert this force upon each
other. The greater the body, the greater is its power of attraction.

"Now, the earth is an immense mass o