Lucy.—(Holding John by the arm.)—"Brother, how can you think of it? The elm is more than eighty feet high! Papa, I beg of you, not to allow it."
Father.—(Calmly.)—"No one shall get up the tree and risk his life, for a thing which certainly is not there."
"There is no thief like a magpie," repeated John, looking at the nest, which might be seen through the higher branches of the tree; "but I confess it would not be easy to reach it. These branches are very long and very slender!"
William, who had said nothing as yet, but had been walking backwards and forwards, with his head down, and his hands in his pockets, turned suddenly round to Mary, and said, "I have been thinking we can soon know if your knife is in the nest. We only want a polemoscope for that. Hurrah! long live optics!"
"A lemoscope!" said Lucy, "What is that? Is it a long hook?"
William.—(Smiling rather contemptuously.) "Poor sister! What ignorance!"
Father—"William, speak kindly—tell your sister what this instrument is, and what you want to do with it."
William.—(Scientifically.)—"In war, when a besieged garrison wishes to know all the movements of the enemy, without being seen, they erect behind the walls, or the ramparts, a mirror, placed at the end of a long pole, and inclining towards the country. You understand, then, that everything that takes place outside, is reflected in the mirror, and can be seen from within, or in another mirror placed at the bottom of the pole, and sloping inwards. This, Lucy, is what is called a polemoscope—that is to say, an instrument for observations in war."
"Thank you, William," said Lucy, "but what are you going to do with it?"
William.—"The thing is quite plain. I am going to fasten a small mirror on a light pitchfork, inclining it downwards. This pitchfork I shall fasten firmly to pole; then some one will climb, dear papa, without any danger, as far as the strong branches reach; from thence he can draw up the pole and its mirror, with a long string, and by raising the mirror above the nest, he will enable us to see, with the aid of your telescope, all that the nest contains. This is my plan, and I think it is not so bad!"