How many slams in an old screen door? / Depends how loud you shut it.

The symbolic representation of Maxwell's equations is introduced to make it easier to survey the whole subject and to formulate the equations. The Feynman diagram method is applied to the computation of the correlation of the fields at different points in space to any order of approximation.

A few useful things […] compose their intellectual possessions.

By using the utmost tact and persuasiveness, he was inducing his uncle to cough up very grudgingly a small quarterly allowance.