Their mother opened the largest paper, and read as follows:—
"We took a tuft of down, tied to a thread, and held it in the cracks and places that the air came in at, to see which way it went. We held it at the window, and it blew in very strong. At the bottom of the door, it blew in very strong too; but at the top, it blew out, into the entry. So, when the entry is full of cold air, and this room full of warm, the cold air will press in and drive out some of the warm air, into the entry.
Rollo."
The other paper was also in Rollo's handwriting, and was as follows:—
"If the entry was full of water, and the parlor full of air, and the walls were water-tight, and you were to open the door between the two rooms, the water would flow into the parlor down below, and the air would flow into the entry up above. We tried it with a tuft.
Nathan."
QUESTIONS.
Why were Rollo and Nathan at first glad to see the rain? What did their mother say to herself on the second day, when she observed their weary and listless appearance? What did she at first direct them to do? How did she prepare the downy tuft? What experiments did they perform with it? Where did they find that the air came in which crowded the warm air up the chimney? What experiments did they perform when the door was opened? Which way did they find that the current of air was setting at the lower part of the door-way? Which way did the current set at the upper part of the door-way? What did Rollo write in his exercise? What was written in Nathan's exercise?