a method of instubstantiating

The window fan knows the secret to disappearing. At rest, it appears as a five-petaled flower, or as a person: head, arms, and legs all the same size and shape, not quite Vitruvian Man. But then a breeze takes it and it spins, and spins faster, until ... it is a blur. Here it's not spinning all that fast, but when it does, then you can see it vanish--which is to say, then you can see that you can no longer see it.

The same thing happens with children. They spin round and round faster and faste...