In the original concept of Volterra, the Burgers' vector of a crystal dislocation is a

translation vector of the crystal, that is, a vector that connects atom positions so that the

crystal can be rejoined perfectly across its glide plane. Such a dislocation is called a total

dislocation. The element of slip it induces carries an atom in the glide plane from one

atom position to another. Only total dislocations can be true two-dimensional defects. If

the Burgers' vector were not a translation vector of the crystal the slipped surfaces would

not weld perfectly together across the glide plane and a planar, surface defect would be

left behind whenever the dislocation moved.