"Electromagnetic theory is a peculiar subject. The peculiarity resides not so much in the stratification - superposed layers of electrostatics. magnetostatics. steady currents and time-varying fields - as in the failure that has attended all attempts to weld these layers into a logical whole. The lowest layer. electrostatics. defines certain concepts. such as E. D,, in a way that is generally satisfactory only for the static case. Yet the attempt is made to force these specialised definitions into the higher strata, with ad hoc modifications when necessary. The student, in looking through his...