What does thoreau mean when he says that the pond "is a mirror which no stone can crack"?

Which two sentences are written in subjunctive mood? take this money and go buy some clothes for yourself. i was happy because i passed the test, which i studied for. if only my umbrella would fix itself, then i could go out in this weather. i'm going on a trip to canada, but i'm not taking you with me. if i were the thief, i would have turned myself in before i got caught.