Abstract
The work of Peierls and Nabarro is extended to a family of edge dislocations of greater widths. The weaker the shearing forces between adjacent atoms in the slip plane, the wider is the dislocation. The external shear stress required to move the dislocations is extremely sensitive to the width, becoming vanishingly small at widths of the order of three atomic spacings. The theory is applied to bubble raft dislocations, and satisfactory agreement is found with experiment.