"Then it sailed slowly away."—[Page 85].
"What, the science of air?" said Rollo.
"Yes," said his father, "the science which treats of air, and of all other compressible and expansive fluids. But let me think. I must try to tell you something which Nathan can understand and be interested in. If I had a very light feather, I could let him perform an experiment."
"Would a little down do?" said Rollo's mother.
"Yes," replied his father, "that would be better than a feather."
Mrs. Holiday then went and brought a little down, and handed it to Rollo's father. Now, there was a lamp upon the table, of a peculiar kind, called a study lamp. It had a glass tube, called a chimney, around the wick, and consequently around the flame itself, being round, like a ring.
Rollo's father told Nathan to hold the down over the top of this glass chimney, and then to let it go.
Nathan did so. The little tuft of down was wafted up into the air, quite high above the lamp, and then it sailed slowly away, and fell down upon the table.
"I know what makes it rise," said Rollo. "It is the heat. The heat makes it rise."
"Do you think so?" said his father. "Then take the down, and lay it gently upon the hearth, before the fire, as near as you can."