Not being a werewolf himself, Childermass wouldn't know whether he smelled any different to the other man or not. But if he can tell a human from a witch, then Childermass is bound to smell like magic. He may only be Norrell's man, and not a coven leader himself, but the magic within him is anything but weak.

Childermass leans forward, putting his chin on his hand, in something of a mirror of the other man's regarding him. "Only something?" he asks, with a wry smile that says he could mean anything by the question. He could be honestly interested in the answer. He could be concerned about the other man. He could have no opinion in the matter at all. It's rather hard to tell, at face value at least.