Evidence Levels: How to Read an Entry

Every entry on From the Surviving Record separates three kinds of statement: points confirmed by independent sources, things a single source records, and inference. The line at the top of each entry links here. This page explains the three marks, how sources are ranked, and how dates, figures and tables are checked.

Fix: confirmed by independent sources

In navigation, a fix is a position confirmed by observation rather than estimated. On this site, a paragraph that opens with Fix: states a point that two or more independent sources support.

Independence is the test. The same figure in two separate sources counts, and so does the same result from two independent calculations. Two passages from one report do not, and neither does a later writer repeating an earlier one.

Fixes are rare because the test is strict. A fix describes the state of the evidence, not a final judgment, and it is withdrawn, with a logged correction, if a source behind it turns out to be wrong.

According to: one source

A statement with only one source behind it is written as an attribution: “according to the 1915 inquiry”, “the log records”, “as the inquest heard”. The wording keeps two things apart: what a source claims, and what can be confirmed.

A primary record shows that someone wrote something down at the time. It does not show that what they wrote was true. Participant testimony, early accident reports and colonial-era journals in particular are never taken at face value.

By dead reckoning: inference

Before satellite navigation, a ship's position between fixes was worked out by dead reckoning: from speed, heading and time elapsed. On this site the phrase marks reasoning that goes beyond what the records state.

A paragraph marked By dead reckoning says what it rests on and what it cannot settle. Every analysis of the last good decision belongs to this level, because it asks what might have happened, which no record can show.

Which source outranks which

The order depends on what kind of statement is being made.

For direct quotations and for who said what at the time, the wording is checked against the original document: the log, the transcript, the report itself. A quotation found in a later book does not stand in for the original.

For events, figures and causes, a single primary record is weighed against physical and archaeological evidence, later scholarship and revised editions of reports. The order is:

1. Independent sources that agree with each other.
2. Refereed scholarly publications and official final reports, including their revisions.
3. A single primary record.
4. Museum explainer pages.
5. Encyclopedias and press summaries.

Encyclopedia articles are used only as leads to other sources and are never listed as sources themselves.

Some statements always need a listed source: every date and time; every death toll and headcount; sums of money, tonnages and dimensions; direct quotations; any sentence of the form “it sank because”; and any claim that something was the first, the last or the only one.

When the sources disagree

Disagreement is written into the entry, not smoothed over. Each version is set out with its source and the point where they part ways. Where counts differ, the entry gives the range and says who gives which figure.

Dates, distances and conversions

Every date, distance and conversion on a page is recalculated from the sources that page lists, and the tables behind them are free to download and check.

In practice, the events in a timeline are put in order from the dates the sources give, and the gaps between dates are counted from those same dates. Distances are recomputed from the coordinates given. Conversions between units, such as tons, nautical miles and kilometers, or feet and meters, are worked out again rather than copied. The values on an entry's registry card are checked against the same figures in the text.

Recalculation catches errors of arithmetic and presentation. It cannot catch a wrong input; that depends on the sources.

Tables you can download

Where an entry rests on a table, the table is offered as a CSV file beside the entry. Each row names its source, where in that source the figure appears (page, chapter or folio) and a link where one exists. Qualifiers such as approximate, attributed or reckoned sit in their own column, so a row read on its own still says how firm it is. A note beside each file states its license and where its columns come from.

The tables are built only from material that may be shared again: public-domain documents and openly licensed data. Sources whose terms allow no commercial reuse are summarized and linked in the text, never copied into a table.

Sources that could not be read in full

Some studies are not available to this site in full. These are cited at the level of the bibliography, author and title, with wording such as “has been argued in”. Their detailed conclusions are not restated, and no summary at the top of an entry rests on them.

Pictures

Every photograph and archival image traces to the page it came from, with its creator and license in the credit line. Diagrams of routes, timelines and measurements are drawn from data, not traced from other people's drawings.

Images marked Illustration are scenes drawn for this site. They carry no evidence, and they never stand in for a real ship, artifact, person or historical image.

What stays out

Quotations, anecdotes and dramatic details that cannot be traced to a primary source stay out of the text. So do investigations, lawsuits and searches still under way, and fraud allegations against anyone living.

If an entry falls short of any of this, the contact page explains how to report it, and every correction is logged on the corrections log.