Trying to Remember the List of Cloud Types

As I was going through them, the cirrus and the nimbostratus, with its white steps like the descending marble ones in my dream last night, I tried to imagine all the forms vapor takes as it rises into the cold, before it is classified. Certainly we must have missed a few. I bring this problem to my father, but he is busy himself, his hands are full, trying to remember how many ounces of sand were equal to an hour in the Middle Ages. I wonder, he murmurs, if I should subtract a few grains, to account for the time it took someone to notice the hour was spent, cross the room, and turn the hourglass over. But if timekeeping used to be inconsistent so that sometimes before the past was repeated a man could exist in one of these pockets for a few moments, uncounted, unregistered, why, I ask, should we correct such a beautiful error? Quite right, says my father, then we should allow the same freedom to your vapor.