material of one trade is, as we say, the finished product of
another. The demand for one thing gives rise to a demand for other
things, for the labor with which to make them, and so on in an
expanding circle. A sympathy, subtle and intense, unites the business
world, and a wave of depression or animation arising in any quarter
may spread itself far and wide, heightened by the gusts of human hope
and fear, and continue long before its influence is spent.

Here we are upon the threshold of one of the most striking and
formidable of economic facts, the regular alternation of periods of
good and bad trade, each very widespread, if not world-wide, in its
range, each comprising certain regular phases of acceleration and
decay, and each infallibly yielding sooner or later to the other. The
details of these phenomena are highly complex, some of them obscure;
an immense literature has already been devoted to the subject, yet its
systematic study is hardly more than begun. The account given in the
preceding paragraph is incomplete and meagre. It is inserted here in
the hope that it will impress the reader with a sense both of the fact
of these alternations and of the deeply rooted nature of the causes
from which they spring. They take a heavy toll of human happiness and
wealth; and there is no object that more urgently calls for concerted
human effort than that of mitigating them, and of alleviating the
misery which they bring in their train. Still better, of eradicating
them if that is possible; but let none suppose that it can be lightly
done. Meanwhile, let us always remember that they form the atmosphere
and medium in which the enduring tendencies of the business world must
work themselves out. It is often convenient to speak of "normal
conditions" in this trade or that; but hardly ever can it be truly
said of a particular moment that conditions are normal. The normal is
rather a mean level about which oscillations to and fro, round and