  A finite-length magnetic vortex line solution is derived within the context
of (4-dim) dilaton gravity. We approach the Bonnor metric at the
Einstein-Maxwell limit, and encounter the "flux tube as (Euclidean) Kerr
horizon" at the Kaluza-Klein level. Exclusively for string theory, the magnetic
flux tube world-sheet exhibits a 2-dim black & white dihole structure. (The
figure has been cut off, and is now available upon request from
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