  It is known that electric-magnetic duality transformations are symmetries of
the generalized Witten-Dijkgraaf-Verlinde-Verlinde (WDVV) equations. In
Seiberg-Witten theory the solutions to these equations come in certain sets
according to the gauge group. We show that the duality transformations
transform solutions within a set to another solution within the same set, by
using a subset of the Picard-Fuchs equations on the Seiberg-Witten family of
Riemann surfaces. The electric-magnetic duality transformations can be thought
of as changes of a canonical homology basis on the surfaces which in our
derivation is clearly responsible for the covariance of the generalized WDVV
system.
