Graviation, electromagnetism and quantized charge: the Einstein insight

A unified field theory of gravity and electromagnetism is presented in which the quantization of charge occurs as a topological property and the electron is represented by a homotopically invariant structure in the field. Chapter titles are as follows: the creative role of mathematics, historical perspective, failure of the mechanical approach, quantum of charge and the nature of the matter field, charge as structure in the matter field, integral representations of the total charge, field equations, electric current density, and remarks and speculations. 8 figures