Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it.
Source: Literary Lapses, `A Manual of Education'
-- Stephen Leacock, (Dec 30 1869-1944), Canadian author, educator, economist, humorist; He was an economic professor noted for popular humor books, literary biographies.