  The quantum-mechanical expression for the polarization of a crystalline solid
does not bear any resemblance to the (trivial) expression for the dipole of a
bounded crystallite; and in fact it has been proved via a conceptually
different path. Here I show how to alternatively define the dipole of a bounded
sample in a somewhat unconventional way; from such formula, the crystalline
polarization formula -- as routinely implemented in electronic-structure codes
-- follows almost seamlessly.
