“A four-sided figure, in which the sides are all equal, and its angles all right angles.”
“Good again: but let me see whether you have a correct notion of the nature of an angle.”
“An angle is the opening formed by two lines meeting in a point.”
Mr. Seymour here acknowledged himself perfectly satisfied with his son’s answers, and said, that he should accordingly direct his attention more particularly to Louisa and Fanny; and, taking his pencil, he sketched the annexed figure.
“You perceive, Louisa,” said her father, “that the line A C makes two angles with the line B D, viz. the angle A C D and the angle A C B; and you perceive that these two angles are equal to each other.”
“How can they be equal?” cried Fanny, “for the lines are of very different lengths.”
“An angle, my dear girl, is not measured by the length of the lines, but by their opening.”
“But surely,” said Louisa, “that amounts to the same thing: for the longer the lines are, the greater must be the opening between them.”
“Take the pair of compasses,” replied her father, “and describe a circle around these angles, making the angular point C its centre.”