How did the rear two torpedoes fire?

They were aimed off of the center line of the boat. How did they aim the back two torpedoes before firing them? Was there some sight that they used on "the bridge" that would allow them to realign the boat's bearing? I would appreciate it if someone could walk me through it.

I'm also curious just about the firing mechanism itself. How did they launch the torpedoes out of the tubes? Was it a spring? Compressed air? A small explosive charge?




I want the doctor to take your picture so I can look at you from inside as well.