A ball thrown up so as to land on the platform at the top of the tower rolled down into the interior, fell on a rapidly revolving disk, was hurled through one or other of the numerous apertures pierced in the cylindrical casing, and had to be caught.
There are no more uses of "aperture" in the book.
Show samples from other sources
The higher the f-stop, the more closed the camera’s aperture.
It wandered along the crest of the hill and terminated before a fragment of wall pierced by a rough aperture which had once been a door.