In the 19th century, MP Samuel Plimsoll campaigned for load lines to be painted on the side of ships to prevent them being overloaded and sinking.

Load lines are painted on the side of ships to show how low it may safely rest in the water without the risk of sinking. Although usually associated with the British MP Samuel Plimsoll (1824–1898), who campaigned for more safety at sea, seafaring societies had marked the sides of their ships hundreds of years earlier.

Why should a ship not be overloaded?

When merchants began to transport goods by sea, they soon realised the importance of loading their ship correctly. If a ship was overloaded it could sink in heavy seas or rough weather. In the 19th century, overloading and poor repair made some ships so dangerous that they became known as 'coffin ships'.

When were load lines first used?

Ships from Venice were protected in this way by the marking of a cross, the traditional symbol of salvation, as long ago as the 12th century but it was not until the 19th century that the use of load lines became widespread.

Why did safety become more important in the 19th century?

During the 19th century, British trade was growing rapidly. The large number of ships being wrecked each year caused greater and greater concern. One of the first attempts to get ships to carry loading marks for safety was made in 1835 by Lloyd's Register, a classification society. Lloyd’s Register introduced freeboard tables for loading, but these only applied to those ships classed by Lloyd's Register itself. Other ship owners could still do as they pleased.

Did sailors worry about the dangerous condition of ships?

Yes, and many refused to go to sea. In 1855, a group of sailors wrote to Queen Victoria complaining that they’d been found guilty of desertion because they’d complained about going to sea in dangerous ships. Around the same time, an inspector of prisons reported that nine out of 12 prisoners in the jails of south-west England were sailors, imprisoned for 12 weeks for refusing to sail in ships they considered to be unseaworthy.

How did Samuel Plimsoll become involved?

In 1870, Samuel Plimsoll, an MP and coal merchant, began to investigate the safety of ships and found the problem worse than he expected. He campaigned in parliament and in 1872, a Royal Commission on Unseaworthy Ships was set up to look at evidence and recommend changes.

When did load lines become compulsory?

The Merchant Shipping Act of 1876 made load lines compulsory, but it wasn’t until 1894 that the position of the line was fixed by law. In 1906, foreign ships were also required to carry a load line if they visited British ports. Since then, the line has been known in Britain as the Plimsoll Line.

How does the load line work?

It is painted on the side of merchant ships. When a ship is loaded, the water level isn’t supposed to go above the line. However, the water can reach different parts of the line, depending on its temperature, saltiness, time of year and geographic location. The basic symbol, of a circle with a horizontal line passing through its centre, is now recognised worldwide.