In the early nineteenth century, despite many individual advances in knowledge, there was no inkling of a comprehensive theory of electricity and magnetism. In developing this, Maxwell pointed the way to the existence of the spectrum of electromagnetic radiation. Defining fields as a tension in the medium, he stated his belief in a new concept - that energies resides in fields as well as bodies. This pointed the way to the application of electromagnetic radiation for such present-day uses as radio, television, radar, microwaves and thermal imaging.
Maxwell made fundamental contributions to the development of thermodynamics. He was also a founder of the kinetic theory of gases. This theory provided the new subject of statistical physics, linking thermodynamics and mechanics, and is still widely used as a model for rarefied gases and plasmas.