There were either two "William H. Howell's" from Fulton County, or we may be related! The William H. Howell I'm related to was the younger brother of Captain Evan P. Howell of Howell's Battery, Ga Light Artillery. I've found records that show that 'my' family's William H. Howell was the 1st Sergeant in his other brother Albert's unit, Company A., Georgia State Line.
It'd be a small world if there were two "William H. Howells" from Fulton County, but not impossible. Was 'your' William the son of Clark Howell of Atlanta's Howell's Mills? If so, we're cousins.
I don't recognize any of the other Howell names from the 19th Regt.
B8B