In an extreme mass-ratio binary black hole system, a non-equatorial orbitwill list (i.e. increase its angle of inclination, {\iota}) as it evolves inKerr spacetime. The abutment, a set of evolving, near-polar, retrograde orbits,for which the instantaneous Carter constant (Q) is at its maximum value (Q_{X})for given values of latus rectum (l) and eccentricity (e), has been introducedas a laboratory in which the consistency of dQ/dt with corresponding evolutionequations for dl/dt and de/dt might be tested independently of a specificradiation back-reaction model. To demonstrate the use of the abutment as such alaboratory, a derivation of dQ/dt, based only on published formulae for dl/dtand de/dt, was performed for elliptical orbits on the abutment. The resultingexpression for dQ/dt matched the published result to the second order in e. Webelieve the abutment is a potentially useful tool for improving the accuracy ofevolution equations to higher orders of e and l^{1}.
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