“Science, child, is knowledge of a lofty and abstruse nature, developing itself in wonderful inventions—gunpowder, for instance, is made by science.”

“Indeed it is not,” said Ratty; “I never saw his name on a canister. Pigou, Andrew, and Wilks, or Mister Dartford Mills, are the men for gunpowder. You know nothing about it, gran.”

“Ratty, you are disrespectful, and will not listen to instruction. I knew Kirwan—the great Kirwan, the chemist, who always wore his hat—”

“Then he knew chemistry better than manners.”

“Ratty, you are very troublesome. I desire you listen, sir. Kirwan, sir, told me all about science, and the Dublin Society have his picture, with a bottle in his hand—”

“Then he was fond of drink,” said Ratty.

“Ratty, don't be pert. To come back to what I was originally saying—I repeat, sir, I am at twelve paces from my object, six from the mirror, which, doubled by reflection, makes twelve; such is the law of optics. I suppose you know what optics are?”

“To be sure I do.”

“Tell me, then.”

“Our eyes,” said Ratty.