From the late 1870s until his death in 1901, the Irish physicist G. F. Fitzgerald was one of the most active and influential proponents of Maxwell's theory of the electromagnetic field. Along with Oliver Lodge, Oliver Heaviside, Heinrich Hertz, and other ‘Maxwellians’, Fitzgerald took the lead in extending Maxwell's theory, clarifying its expression, and subjecting it to experimental test. The surviving correspondence of this Maxwellian circle provides a window into the workings of late Victorian physics and into the private side of scientific communication.