In 1867, Plimsoll was elected as the
Liberal Member of Parliament for
Derby, and endeavoured in vain to pass a bill dealing with the subject of a safe load line on ships. The main problem was the number of powerful ship-owning MPs in Parliament. In 1873, he published a book entitled
Our Seamen. It became well known throughout the country discussing the dangers of 'coffin ships' (ships that were highly insured in case of sinking, with minimum consideration given to seafarer safety). These ships were said to be overinsured and overloaded as a result. Disraeli moved that he be reprimanded, but on the suggestion of
Lord Hartington agreed to adjourn the matter for a week to allow Plimsoll time for thought. Eventually Plimsoll made an apology. Many people, however, shared his view that the bill had been stifled by the pressure of the shipowners, and popular feeling forced the government to pass a bill in 1876 was amended into the
Merchant Shipping Act. on
Victoria Embankment, London This gave stringent powers of inspection to the
Board of Trade, and the mark that indicates the safe limit to which a ship may be loaded became generally known as
Plimsoll's mark or line. The improvements in safety resulted in fewer ship sinkings and seafarer deaths, with Plimsoll's reforms credited as "saving the lives of countless seaman." Plimsoll's reforms would go on to have a significant international effect in the 20th century, eventually resulting in the 1930
International Convention on Load Lines. Plimsoll was re-elected for Derby at the UK
general election of 1880 by a great majority but gave up his seat to
William Vernon Harcourt, believing that the latter, as Home Secretary, could advance sailors' interests more effectively than any private member. Offered a seat by 30 constituencies, Plimsoll was an unsuccessful candidate in
Sheffield Central in
1885. He did not re-enter the house, and later became estranged from the Liberal leaders by what he regarded as their breach of faith in neglecting the question of shipping reform. He was for some years the honorary president of the
National Sailors' and Firemen's Union, and drew attention to the
horrors of the cattle-ships, where animals were transported under appalling and over-crowded conditions. ==Later life==