My favorite passage from Northanger Abbey (Dover Thrift Editions) . Henry Tilney has taken upon himself to instruct Catherine Morland about the aesthetics and the theory of the picturesque:

“Delighted with [Catherine’s] progress, and fearful of wearying her with too much wisdom at once, Henry suffered the subject to decline, and by an easy transition from a piece of rocky fragment and the withered oak which he had placed near its summit, to oaks in general, to forests, the inclosure of them, waste lands, crown lands and government, he shortly found himself arrived at politics; and from politics, it was an easy step to silence.”