What separated Amphions from Leanders?

What was the difference between the Leander and Amphion classes?

The Amphions combined unit machinery, a longer two-funnel hull, revised armour and arrangement, and numerous internal changes behind a superficially similar appearance.

Unit machinery, hull length, two funnels, revised armour and arrangement, and numerous internal changes distinguished the Amphions from the Leanders. Their similar external appearance concealed substantial differences inside. The machinery arrangement aimed to keep a single torpedo from disabling the whole ship. These changes affected damage tolerance as well as the ships' classification.