The brush is needed to whisk eraser dust away. The chief advantage of this eraser is that it may be sharpened to a point to erase a very small area.

and when the great raines or water cometh and ſinketh thorow the gravell, and cometh to the earth, then the earth ſwelleth and bolneth, and waxeth ſoft, and with treading, and eſpecially with carriage, the gravel ſinketh and goeth downwards; […]

Such mechanisms, based on postsegregational cell killing, are also typical for other toxin-antitoxin modules that participate in maintenance of many bacterial plasmids.

The worst that can—and has—been said about Memento is that it’s an airless gimmick, visually undistinguished, and not even all that sophisticated when the puzzle pieces are finally put together.