Suppose you were to make a cake, an ordinary sized cake, you know, how much yeast would you put in it ?" "Not any, papa," said Patty, laughing merrily.

"I know enough housekeeping not to put yeast in a cake.

I'd use baking-powder." "Yes," said her father, quite undisturbed, "that is what I meant,--baking-powder.

Now how much of it would you use ?" "Well, about two teaspoonfuls," said Patty, feeling very important and housewifely.
"Yes.

Now suppose instead of two teaspoonfuls you put in two cupfuls." "Why then I wouldn't have any cake at all! I reckon it would rise right up the chimney and run down on the roof outside." "Well, that shows just what I mean.