I The Force of Gravity -- II Fields of Force -- III The Potential -- IV The Divergence Theorem. -- V. Properties of Newtonian Potentials at Points of Free Space -- VI. Properties of Newtonian Potentials at Points Occupied by Masses -- VII. Potentials as Solutions of Laplace's Equation; Electrostatics -- VIII Harmonie Functions -- IX Electric Images; Green's Function -- X Sequences of Harmonie Functions -- XI Fundamental Existence Theorems. -- XII The Logarithmic Potential -- Bibliographical Notes.