The overwrite, administered
Everything above this line is unattended. You read it once, on the way down, and that was the last time you will look at it — the page is fairly confident of this, and is acting on it. Four words up there will change while you are below them. Not secretly: each one is listed at the foot of this page beside the word it displaced. You still will not catch it happening. That is not a boast about the mechanism, which is crude. It is a fact about reading, and you are the one supplying it.
Disclosures first, as always. About thirty lines of hand-written JavaScript — in the source, along with every original word, sitting in plain sight on the elements that are about to lose them — watch four marked spans. A word is rewritten only when it has been on your screen and has then gone off the top of it: it must have been in front of you, and it must now be behind you. Nothing is measured, stored, or sent anywhere; the page cannot tell whether you noticed, and there is no score. Two honest caveats. If you never scroll, nothing changes — leave no sentence behind and nothing behind you can be altered, which is either a perfect defence or a description of never finishing a page. And the trigger is screen position, so if you are reading by ear rather than by eye, the words may go while your attention is somewhere this page has no way of seeing.
Knowing is not a defence. The instruments in this atlas keep arriving at that sentence and it keeps holding. You cannot stand guard over the paragraph above, because guarding it would require a copy of it, and you do not have one. What you have is its gist — a shape, a direction, two or three words that did some work. The rest was never taken in the first place. The eye reads sharply over about the width of a thumbnail held at arm's length, and moves; the sensation of a whole page in focus is a promise the visual system makes and never has to keep, because the page is right there and can always be looked at again. That arrangement is sound, and universal, and this instrument is a small breach of it. It changes the thing you would look at, in the interval when you are not looking.
A thread runs through this atlas called the null entry: what the senses stop reporting is not lost but filed as the zero that everything else gets measured from, and the file is opened only by an interruption — a fridge stopping, a friend's hallway, a light switch the fingers have learned. This page looks like a member of that thread and is not one, and the second clause is where it fails. Interruptions are scheduled here — four of them, each a word swapped for a different word — and not one of them opens a file. Nothing opens because nothing was filed. Habituation is a decision to stop reporting a signal you are still receiving; this is the absence of any record to report against. The null entry describes a thrifty archive. This describes a room with no archive at all, whose furniture may be moved freely, provided it is moved behind your back.
So where is the text? On the page. That is the whole arrangement, and it is not a failing: a reader delegates custody to the surface, the surface holds still, and between them they perform something that looks from outside exactly like a person remembering a paragraph. The pocket, in other words, is the page. Every reader alive is trusting a flat object not to change its mind, and nearly every flat object honours it — books, signs, the label on a jar — with one class of exception, which is growing, and of which this page is a rude little instance.
The list below fills as it happens. When you have read it you will have a choice: go up and look, or take the list's word for it. Most readers take the word — which is the same trust that let the page do this in the first place. It is not misplaced, exactly. It is just never checked.