Why Archer carried sponson-mounted guns

Why were the Archer class's six-inch guns mounted in sponsons rather than behind simple broadside shields?

The arrangement produced strong forward and after fire for contemporary close-action tactics while retaining a useful broadside.

The sponson-mounted six-inch guns gave the ship strong arcs ahead and astern as well as a useful broadside. Forward fire still mattered in an era shaped by recent close-action battles and lingering expectations of ramming attacks. Archer would use its bow torpedo rather than ram directly, but the tactical geometry still favoured weapons that could bear while closing. The arrangement allowed four guns to fire forward, four aft, and three on either broadside through overlapping arcs. A full sailing rig added a separate form of insurance by offering limited mobility if a cruiser exhausted its coal far from support.