APPENDIX A

                            GRAVITY THEORY





Gravity exploration is based on Newton's law expressing the force



of attraction between two particles in terms of their masses and



separation (Dobrin, 1976).  This law of gravitation which defines



this attraction is stated as:  F=Gm1m2

                                  r2



where      F=force of attraction between m1 and m2 due to gravity



           G=universal gravity constant



           m1=mass of the earth (considered concentrated at its center)



           m2=mass of particle on earth's surface



           r=radius of the earth



                         (Nettleton, 1976)



The force F which represents the force of gravity is not the



measurement that is used in exploration.  In exploration, the



acceleration of a body resulting from that force is the



conventional quantity used to measure the gravitational field



acting at any given location (Dobrin, 1976).  This acceleration



can be derived from Newton's Second Law of Motion:



                             F=m2a



where     a=acceleration of the body due to gravity



                               62