Peter A. Davidson

“naturally think in vectors. They know nothing of their formal manipulation, but if they think about vectors, they think of them as vectors, that is, directed magnitudes. No ignorant man could or would think about the three components of a vector separately, and disconnected from one another. That is a devise of learned mathematicians, to enable them to evade vectors. The device is often useful, especially for calculating purposes, but for general purposes”
― Peter A. Davidson, An Introduction to Electrodynamics

“electrical conductivity of the solid and μ its permeability. On the other hand, the propagation of many (but certainly not all) types of waves is governed by the so-called wave equation. For example, small-amplitude”
― Peter A. Davidson, An Introduction to Electrodynamics