Snape's eyebrows rose. Finding out something new at a time like this was a surprise, and a pleasant one at that. He expressed his appreciation by admitting his former ignorance, "I didn't know spiders could do that."
He watched, frowning with uncertainty at the odd signs of pressure on the ground, then he realised that Al had stretched out at full length on the ground.
From anyone else it would have seemed an utterly bizarre thing to do. But coming from Al, it was natural, in fact oddly comforting.
Reading time. Snape had seen him often enough, curled up, cradling a book on his lap, happily lost to the world. There was something strangely endearing about that depth of focus.
By now, the last few Muggles had straggled away from the site, leaving the now thoroughly extinguished ruins for their beds. The night was quiet, except for the faint night breeze, rippling in the grasses.
Something about the deep evening hush made Snape hold his breath, the better to listen...