how to determine the relative differences in activity between metals
You have a standard pot of liquid electrolyte into which are dipped non-touching same-spaced paired strips of different clean metals.  The external circuit between the strips is a sensitive voltmeter (with extremely high electrical resistance - hard by zero current flow).  You measure the potential (noting direction!) between all combinations of paired strips, (n)(n-1)/2, and then draw certain conclusions.

Why are amalgams saturated with respect to excess solid metal interesting substrates for this experiment (e.g., aluminum)? How do you construct a standard hydrogen electrode?