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

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