
The equation is the bipolar equation of the Cayley's oval. Arthur Cayley (18211895) studied the curve in 1857. The curve is formed in nature as the equipotential lines ^{1)}
in an electromagnetic or gravitational field.
And together in one field: 1) While the force is of the form F = k/r^{2}, the potential has the form V=k/r. 2) Realize that r_{1}^{2} = (x+1)^{2} + y^{2}, r_{2}^{2} = (x1)^{2} + y^{2} 