On the afternoon of July 22, 1875, Samuel Plimsoll rose in the House of Commons to beg the government not to abandon the shipping bill he had spent two years fighting for. Prime Minister Benjamin Disraeli had just told the House there was no time left that session to pass it. Plimsoll named a shipowner sitting among the members, accused the chamber of sheltering men who sent sailors to death for profit, and when the Speaker ordered him to withdraw the word "villains," refused three times. A week later he apologized for his language while explicitly declining to withdraw any statement of fact, and the House discharged the reprimand it had been on the point of ordering.
What Plimsoll described had a name on the docks: a coffin ship, an old, worn-out hull that was over-insured, overloaded, and sent to sea anyway, sometimes deliberately scuttled for the insurance money. Outside the fleet Lloyd's Register inspected and classed on its own, nothing on a ship's side told a sailor, a dockworker, or an underwriter how deep was too deep; only the owner's word did, and the owner had a reason to lie. Plimsoll told the House he had gone through the 15,000 vessels on Lloyd's Register and found 2,654 of them had already gone off class and forfeited their rating, sailing on regardless.
Within a month, the Merchant Shipping Act, 1875 gave the Board of Trade's newly appointed inspectors authority to provisionally detain a British ship for survey whenever they believed her unsafe. The same Act, from November 1 that year, required the owner of every British ship entering outward on a voyage overseas to mark her sides with a painted disc and bar, a load line. But the Act did not ask the disc to mark a safe depth. It said only that the disc should show the maximum the owner intended to load her to, his own declared plan, not a calculated limit. The following year's Merchant Shipping Act restated the rule in more detail and extended it to coasters of eighty tons or more, still excluding fishing vessels and pleasure yachts.
Lloyd's Register had kept its own freeboard rule since 1835, three inches of hull above water for every foot of hold depth, but that applied only to ships the society classed, and an owner outside that fleet was free to ignore it. The Board of Trade did not adopt its own buoyancy tables, worked out by the surveyor Benjamin Martell, until 1886, and no law yet compelled anyone to use them or to make the painted disc mean anything but what the owner said he intended. Only the Merchant Shipping Act of 1890 took the line away from the owner's own declaration and gave its position to Lloyd's Register and the other societies the Board authorized to apply its tables.
A mark painted on a hull becomes a fact only once the person who profits from moving it no longer gets to write it himself. It took the Merchant Shipping Acts of 1875, 1876, and 1890 before the line on a ship's side stopped being the owner's promise and became someone else's calculation.