First Use of Periscope in Action?-- Part 1

APRIL 12TH, 1864: The engaement between Porter's ships and dismounted Confederate cavalry at Blair's Landing, Louisiana, also featured what may have been the first use of a periscope in action. //// It had been developed by Chief Engineer Thomas Doughtry of the ironclad USS Osage and later described by Lt.Cmdr Thomas O. Selfridge as "a method of sighting the turret from the outside, by means of what would now be called a periscope...." In other words, he could peer through it from the safety of inside and sight his guns. //// --Old B-R'er