conina identify clouds

"It's just that, well, looking at cumulus clouds from above is - "
"Shut up."
"Sorry."
"Anyway, they're stratus. Strato-cumulus at most."
"Right," said Nijel miserably.
"Does it make any difference?" said Creosote, who was lying flat on his horse's neck with his eyes shut.
"About a thousand feet."
"Oh."
"Could be seven hundred and fifty," conceded Conina.

Sourcery, pg. 270-271