A solution to the more than 300-years old problem of geometric and physical
interpretation of fractional integration and differentiation (i.e., integration
and differentiation of an arbitrary real order) is suggested for the
Riemann-Liouville fractional integration and differentiation, the Caputo
fractional differentiation, the Riesz potential, and the Feller potential. It
is also generalized for giving a new geometric and physical interpretation of
more general convolution integrals of the Volterra type.
Besides this, a new physical interpretation is suggested for the Stieltjes
integral.