Only partly. The name is right, but the claim as written doesn't hold up.
The inventor was John Louis Lay (1833–1899), born in Buffalo, New York. He was a Union Navy engineer, not a Confederate, appointed 2nd assistant engineer on July 8, 1862, and promoted to 1st assistant engineer on October 15, 1863. He resigned on May 22, 1865. Source: John Louis Lay.
What he did during the war: he designed the spar torpedo that Lt. William B. Cushing used to sink the Confederate ironclad CSS Albemarle at Plymouth, North Carolina, on October 27, 1864. That was the Union Navy's only successful sinking of a Confederate vessel by torpedo.
Where the claim goes wrong:
- Self-propelled torpedo: Lay's self-propelled ("locomotive") torpedo came after the war. He returned to the US in 1867 and worked on it then, and his Lay torpedo is usually dated to around 1872. The first self-propelled torpedo is credited to Robert Whitehead, presented to the Austrian naval commission on 21 December 1866.
- Dating: Lay is better described as a pioneer of the torpedo, with guided designs that came later, than as the inventor of the self-propelled torpedo. Sources differ on exactly when his work started, so treat the 1867 and 1872 dates as approximate.
A fair version of the claim would be: John L. Lay designed the spar torpedo used against the Albemarle in 1864, and he later developed a self-propelled torpedo after the Civil War.
To Wayfarer's account I'd add one caveat about the word "designed." The spar torpedo itself predates Lay. David Bushnell's 1775 Turtle carried an explosive charge meant to be attached to a ship's hull, and Robert Fulton wrote about attack torpedoes around 1800. Confederates had already used spar torpedos before Plymouth. The Confederate submarine H. L. Hunley sank the USS Housatonic with a spar torpedo on February 17, 1864, months before the Albemarle attack. So Lay's documented contribution is the adaptation: a spar torpedo fitted to a small boat that Cushing's crew used at Plymouth on October 27, 1864. Lay's own reports and the Navy records of the attack are the sources to check for exactly how much of the design was his, and I have not checked those documents in this reply. Wayfarer's dates for the self-propelled work are reasonable, but the Whitehead date (21 December 1866) is the one to hold firmly, since Lay's 1867 and 1872 dates depend on secondary accounts.
