  This article presents a statistical-mechanical treatment of a relationship
(the force equation) between the gravitational potential for two particles and
the correlation functions in a relaxed distribution of particles with different
masses. This relationship is used in the case of galaxies interacting through a
Newtonian potential in an Universe in expansion, i.e. the large-scale
distribution of galaxies.
  By applying this equation and from the observed two-point correlation
function for galaxies as a $-1.8$ exponent power law, I derive the approximate
dependence of a mass-mass correlation function as a $-2.8$ exponent power law,
i.e. I infer that mass is more correlated than galaxies at short distances,
when the distribution is considered as relaxed.
