“Let us ask Potter how we would tell the difference between an Inferius and a ghost.” The whole class looked around at Harry, who hastily tried to recall what Dumbledore had told him the night that they had gone to visit Slughorn.
“Er — well — ghosts are transparent —” he said.
“Oh, very good,” interrupted Snape, his lip curling. “Yes, it is easy to see that nearly six years of magical education have not been
wasted on you, Potter. ‘Ghosts are transparent.’ ”
Pansy Parkinson let out a high-pitched giggle. Several other people were smirking. Harry took a deep breath and continued calmly, though his insides were boiling, “Yeah, ghosts are transparent, but Inferi are dead bodies, aren’t they? So they’d be solid —”
“A five-year-old could have told us as much,” sneered Snape.
“The Inferius is a corpse that has been reanimated by a Dark wizard’s spells. It is not alive, it is merely used like a puppet to do the wizard’s bidding. A ghost, as I trust that you are all aware by now, is the imprint of a departed soul left upon the earth . . . and of course, as Potter so wisely tells us, transparent.”
“Well, what Harry said is the most useful if we’re trying to tell them apart!” said Ron. “When we come face-to-face with one down a dark alley, we’re going to be having a shufti to see if it’s solid, aren’t we, we’re not going to be asking, ‘Excuse me, are you the imprint of a departed soul?’ ”