"O father," said Nathan, "I could use them; I am pretty strong. I can wheel Rollo's wheelbarrow."
His father smiled. "Very possibly," said he; "but I do not think that you would be strong enough to use wings, even if you had them."
"Why, at any rate, I am stronger than a bird," said Nathan.
"Yes," said his father, "you have more actual strength than a bird, but not more in proportion to your size. You are absolutely stronger, but not relatively."
"What do you mean by that?" said Nathan.
"Why, you have actually more strength than a bird,—a robin, for instance; you could hold him so that he could not get away; and you could lift more than he could too. But then you are a great deal larger, and you are not as much stronger than he is, as you are larger. If you are a hundred times as heavy as he, you are not a hundred times as strong. That's what I mean by saying that you are absolutely stronger, but not relatively. That is, you are not as many times stronger, as you are larger and heavier. You are absolutely stronger, but not relatively; that is, in proportion to your size and weight.
"Now I can prove to you," continued his father, "that you would not be strong enough to fly with wings, even if you had them. Suppose there was a pole fastened across the room, and another pole just above it; could you pull yourself up, from one pole to the other, by your hands alone, without touching your feet?—Or a ladder," continued his father,—"it will be better to suppose a ladder. Now, if there was a ladder leaning up against a building, could you climb up on the under side by your hands, drawing yourself up, hand over hand, without touching your feet?"
Here Rollo, who was reading in a little chair at the back part of the room, when his father first commenced the conversation with Nathan, but who had been listening for a few minutes past to what his father had been saying, jumped up, and came across the room to his father, and said,—
"Yes, sir, yes, sir; I can. I have done it often in the barn."
"How high up could you go?" said his father.