The fire was not built in this room until the party which was to occupy it arrived, but the room became warm very quick. Rollo was surprised that the room became warm so quick, and his father said that such an arrangement as that, namely, a stove standing out upon the hearth, with a pipe above, warmed a room very quickly; and one reason was, that it operated by conduction as well as by radiation, whereas a fire in a common fireplace could only warm the room by radiation. Then Rollo wanted to know what _conduction_ and _radiation_ meant. His father explained them to him while they were waiting for the tea to be brought in.
“There are two ways by which heat moves,” said his father. “One way is by shooting swiftly through the air like light. Hold your hand up before the fire.”
So Rollo held his hand up before the fire as his father had directed.
“Do you feel the warmth of the fire upon your hand?”
“The heat comes from the fire to your hand very swiftly through the air, and makes your hand feel warm.”
“How do you know it comes so swift, sir?” said Rollo.
So his father looked about the room, and he saw a large book lying upon a table between the windows. He got the book, and brought it to the fire.
“Now,” said he, “I will hold the book between your hand and the fire. Then the heat cannot come to your hand.”
So Mr. Holiday held the book between Rollo’s hand and the fire, and Rollo said that he could not feel the heat.
“Now,” said his father, “I will take the book away suddenly, and we will observe what will be the effect. If the heat moves slowly through the air, it will be some time before you begin to feel the warmth; but if it shoots through to your hand quick, you will feel it immediately.”
So saying, Mr. Holiday suddenly withdrew the book.
“Yes, sir,” said Rollo; “I feel it immediately.”
Rollo’s father then told him to go back from the fire as far as he could go, and still feel the heat upon his hand, and then he interposed the book between the fire and his hand just as before. Rollo still found that he could feel the heat from the fire instantly, after his father took the book away.
“Now, that is radiation,” said Mr. Holiday.
“Yes,” said his father. “Heat radiates from a fire, in all directions, through the air. Heat radiates, too, from all bodies that are hot, or warmer than the air around them. Go and hold your hand near the stove pipe, and see if you can feel the heat radiating from the stove.”