Magnetic field lines have neither beginning nor end. Slice a bar magnet and two complete magnets appear; the lines simply close through the fresh faces. ∮ 𝐁⃗ · d𝐀⃗ = 0 The identical surface integral for the electric field equals the enclosed charge, exposing sources and sinks that magnetism has never supplied. Maxwell wrote the magnetic statement into his 1861 paper on physical lines of force, where it stands as one of the four equations that bind electricity and magnetism together.