anxious to ask him some questions about springs, but he would not go up
stairs to disturb him. But after dinner his uncle came into the parlor
where the boys were, and then Samuel asked him where all the water comes
from that flows in the rivers and other streams.

"From the ocean," answered Mr. Harvey. "I suppose you have seen water
boiling, Samuel."

"Yes, sir."

"And have you seen the steam rise up from the water into the air?"
Samuel said that he had. His uncle continued:

"Whenever water is heated, it is turned into steam, or vapor, as it is
sometimes called. If there is enough of heat to make water boil, the
vapor passes off very fast, until the water is gone. Now the sun is
continually changing the water of rivers, ponds, lakes, and of the
ocean, into vapor. This vapor rises. The air about a mile above the
earth, is much colder than it is on the earth; so when the hot vapor
from the ocean meets the cold air, it again becomes water, and forms
clouds. I see you are ready with a question, John."

"Yes, sir," said John. "I cannot see, father, how the clouds can float
in the air if they are nothing but water. Why do they not pour down?"
His father answered:

"I expected this would be your question. The clouds, my son, are water,
but not in a close mass, like that in a bucket or in the mill pond. You
have seen soap bubbles, and know that a great many of them may be joined
together without breaking. It is supposed by learned men, that clouds