The potential theoretic foundations proposed by Hardy for his multiqua
dric-biharmonic method are shown to be either erroneous or deficient f
or the purpose of gravity predictions based on mixed data types. Speci
fically, the discretized model for the potential as a sum of point sou
rces weighted by distance is nonharmonic in free space; whereas, the r
elationships between gravitational quantities (gravity anomaly, geoid
undulation, deflections of the vertical, etc.) are predicated on a New
tonian (harmonic) potential.