  N=8 supergravity has a rich spectrum of black holes charged under the 56 U(1)
gauge fields of the theory. Duality predicts that the entropy of these black
holes is related to the quartic invariant of the E(7,7) group. We verify this
prediction in detail by constructing black holes that correspond to
supersymmetric bound states of 2-branes at angles and 6-branes. The general
bound state contains an arbitrary number of branes rotated relative to each
other, and we derive the condition for these rotations to preserve
supersymmetry. The microscopic bound state degeneracy matches the black hole
entropy in detail. The entire 56 charge spectrum of extremal black holes in N=8
supergravity can be displayed as the orbit under duality of a five parameter
generating solution. We exhibit a new generating configuration consisting of
D3-branes at angles and discuss its entropy.
