Standing Orders
We have never seen another world.
We have only seen light that has been in one.
Two sections, one interface
Skylake Observatory has no containment cells, no armed detail, and no authority to dispose of anything. Between us and the thing we study there is a surface no one has crossed. An observatory is the right comparison: an astronomer cannot touch a star either. She waits for the light, then subtracts the atmosphere.
The Optical Section works the shore. It sees what it cannot hold.
The Custody Section works the store room. It holds what it cannot place.
Objects do come up. They may be received, catalogued, measured, cut, and destroyed. The Custody Section is a laboratory in the ordinary sense, and its records are ordinary laboratory records. What it is not, ever, is a shortcut across the interface. See § 8.
The interface
Skylake holds no water. The medium below the surface matches surface atmosphere in composition, temperature, and pressure gradient. Its refractive index is very slightly higher. The surface is therefore a discontinuity in refractive index, not an air–water boundary.
The first anomaly on record came out of a routine polarimetry run. Brewster's angle at the surface measures 45.03°. For water it would be 53.1°. Eleven repeats agreed. Every assumption that began "since this is a lake" was withdrawn over the following year.
Depth is optical, not spatial
Below the interface there is not one world but many. They are ordered by refractive index. They do not adjoin one another and do not communicate. How deep a world is means how far its index differs from ours, written Δn.
This is not a metaphor. Light bends only on entering a medium whose rules differ from the one it left, and it bends further the further those rules are. Δn is a reading of that difference.
The same number sets how much we get to see. As Δn rises the escape cone narrows: the range of angles at which light can leave that world and reach our side shrinks. Depth is not farther away. Depth is darker. Past a certain Δn the light stops coming out for reasons of geometry alone.
The four strata
A stratum is a classification, not a coordinate. It records what we are able to say about something, not where the thing is.
Shallows
Δn < 0.01 · directly observable
Legible to the eye. Objects are recognisable, and exactly one thing about them is wrong. Every Shallows entry asks the same question: if two things share all their properties they are one thing, so what is a thing that differs in one respect only? Convention: the difference must be single, and it must be quantifiable.
Thermocline
0.01 ≤ Δn < 0.1 · steepest gradient
A small change in depth, a large change in law. Distortion peaks here. Objects from this stratum work — they visibly do something — and the doing cannot be put into local vocabulary. This is not incomprehension. It is the absence of the words. Convention: the record may be exhaustive; the Inference field must read "No translation available."
Deep Water
Δn ≥ 0.1 · escape cone closed
Nothing is visible. We have only what floats up, never the world it floated out of. One further mark: deep water is anoxic, and objects from it do not decay. Something that should have rotted to nothing arriving intact is itself stratum evidence. Convention: no direct observation anywhere in the entry.
Unsounded
Δn does not converge · classification fails
Unsounded does not mean very deep. It means the depth cannot be taken. Not infinite — inapplicable: repeated soundings contradict each other, and the contradictions do not shrink as the instruments improve. This stratum marks the failure point of the scheme itself. Convention: use sparingly. Each use spends the credibility of the other three.
Turnover
Real lakes overturn twice a year. The water column mixes, and stratification collapses until it re-forms. Skylake does the same.
During turnover the strata are disordered. Deep Water material surfaces in the Shallows, Δn readings swing for hours at a time, and the stratum assigned to an existing entry may stop being true. Nearly everything we hold was recovered within forty-eight hours of an overturn.
Turnover is not an accident. It is the only harvest we get.
Normalization
A recovered object's Δn drifts toward the local value. Having arrived here, it begins to keep our rules instead of its own. The anomaly fades. Every object in custody is on a clock.
This is why the store room is full of buttons, rope, ticket stubs, and spectacles. Once normalization completes they are buttons. Nothing is lost that anyone can point to, and the thing we wanted is gone.
The non-decay of Deep Water material is the same effect stalled: the further a thing came, the more it refuses to become one of ours. Depth buys time. Nothing buys more than that.
The Custody Section is therefore not a warehouse. It is a triage ward.
Lost property
An object crossing the surface does not sink. It enters free fall away from the interface. To the world below, we are equally below them, and what they drop falls toward us.
So every recovery here is a loss somewhere else. This archive is assembled entirely from other people's lost property.
Each entry closes with a Loss Note. One line. Do not explain it and do not press on it.
The two rules
One. No entry may contain an observation that did not cross the interface.
Two. An object is evidence, not a conduit.
The first rule holds because no one has been down and no one can go down. Any passage written as we entered, we retrieved, we secured is void.
The second rule is the one that gets broken. You may measure an object as finely as you like, but a conclusion about the world it came from has to come from the interface. You can establish that this lens polarises at 45°. You cannot conclude from it that only one of their eyes needs correcting. The measurement is admissible; the world behind it is not.
Expect people to try anyway. The object is right there and the surface is not, and the shortcut is always available. Note that the most persuasive object is the one that lies best, and that our incident file is made up almost entirely of second-rule cases.
Rigour is what produces the effect here, not vocabulary. Hold these two and a reader will find the depth unassisted; pile on terminology instead and the air goes out of it.