The After Steerage was where the Firing Battery was located. The battery was intended to provide the current to detonate the torpedo (mine) that exploded prematurely on March 5 1880.Interview with Gunner James Tubb,
"How far was the binnacle stand from the battery? - The battery was down below in the after steerage."
"And the distance from there was fourteen feet? - "Fourteen feet horizontally & six perpendicularly."
28 March 1881 Torpedo Accident Report,
mouseover battery and red dot.