SynopsisThis essay concerns an aspect of the speculative contributions of J. J. Thomson to a field of physics somewhat removed from that upon which his popular fame and scientific eminence were alike founded. He published a number of statements in the period 1903–1910 advocating a discontinuous structure of the electromagnetic field. His unorthodox conception of the field was based upon the presumed discreteness of Faraday's physical lines of electric force. While his ideas led to significant experimental work, they were not (...) brought together in the form of a completed theory. It was at this same time that the quantum theory was independently evolving notions of a structure of the field, and Thomson's efforts at developing a theory of light were diverted into a protracted criticism of the hypothesis of quanta. In 1924–1936 he returned to the subject of the structure of light, but these latter speculations no longer had much relevance to contemporary physical thought. (shrink)