Blue light (pyrotechnic signal)

Hunley, the Confederate submarine which became the first to sink an enemy vessel, the USS Housatonic, on February 17, 1864, during the Civil War.

Blue light as made in 1864 has been reproduced according to the two recipes listed in period texts[10][11] and has been tested with success over the same distances involved in the Hunley engagement.

Such displays were also popular in nineteenth century civilian life: two hundred blue lights were used in the first illumination of Niagara Falls during the 1860 North American visit of the Prince of Wales.

[12][13] "Blue Light" was a derisive nickname given to military officers of the 18th and 19th centuries, whose evangelical Christian zeal burned as brightly as its namesake signal, to the chagrin of those less ardent.

[14] During the American Civil War, Confederate General Stonewall Jackson carried the nickname "Old Blue Light" because his men said his eyes glowed with a blue light when battle commenced Shelby Foote, The Civil War; the nickname is referenced in the lyrics of "Stonewall Jackson's Way" (penned circa 1862).