  The paper establishes a correspondence relating two specific classes of
complex algebraic K3 surfaces. The first class consists of K3 surfaces
polarized by the rank-sixteen lattice H+E_7+E_7. The second class consists of
K3 surfaces obtained as minimal resolutions of double covers of the projective
plane branched over a configuration of six lines. The correspondence underlies
a geometric two-isogeny of K3 surfaces.
