  We make an attempt to describe the spectrum of masses of elementary
particles, as it comes out empirically in six distinct scales. We argue for
some rather well defined mass scales, like the electron mass: it seems to us
that there is a minimum mass associated to any electric charge, so we elaborate
on this assumption; indeed, some scales of masses will cover also masses of
composite particles or mass differences. We extend some plausibility arguments
for other scales, as binding or self-energy effects of the microscopic forces,
plus some speculative uses, here and there, of gravitation. We also consider
briefly exotics like supersymmetry and extra dimensions in relation to the mass
scale problem, including some mathematical arguments (e.g. triality), which
might throw light on the three-generation problem.
  The paper is rather tentative and speculative and does not make many
predictions, but it seems to explain some features of the particle spectrum.
