https://en.wikipedia.org/wiki/Coal_torpedo
After the Civil War
Courtenay had traveled to England in 1864 and remained there until 1867, trying to sell the "secret" of the coal torpedo to foreign governments. He approached the British War Office, but they turned him down after he would not agree to allow them to examine his invention before purchasing it.[10] When Courtenay returned to the United States, one or more business partners to whom he had entrusted the secret remained in England. The Times in 1873 reported rumors that disreputable ship owners were purchasing coal torpedoes to put in their own ships as a form of insurance fraud, so that over-insured ships and cargo would sink while far out at sea, leaving no evidence.[13][14] Other reports scoffed at the rumors, suggesting they were false stories planted by supporters of Samuel Plimsoll, a Member of Parliament who was trying to pass a bill reforming the shipping industry.[15] Nothing was ever proven, but the reports stirred up popular interest in various supposed methods of sabotaging ships, and the coal torpedo even made an appearance in the short story, "That Little Square Box", by Arthur Conan Doyle, published in the collection The Captain of the Polestar and Other Tales in 1890.
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