other industries, and if industry A fail and is in difficulty,
industries B, and C, and D, which used to sell to it, will not be
able to sell that which they had produced in reliance on A's demand,
and in future they will stand idle till industry A recovers, because
in default of A there will be no one to buy the commodities which
they create. Then as industry B buys of C, D, &c., the adversity of
B tells on C, D, &c., and as these buy of E, F, &c., the effect is
propagated through the whole alphabet. And in a certain sense it
rebounds. Z feels the want caused by the diminished custom of A, B,
& C, and so it does not earn so much; in consequence, it cannot lay
out as much on the produce of A, B, & C, and so these do not earn as
much either. In all this money is but an instrument. The same thing
would happen equally well in a trade of barter, if a state of barter
on a very large scale were not practically impossible, on account of
the time and trouble which it would necessarily require. As has been
explained, the fundamental cause is that under a system in which
everyone is dependent on the labour of everyone else, the loss of
one spreads and multiplies through all, and spreads and multiplies
the faster the higher the previous perfection of the system of
divided labour, and the more nice and effectual the mode of
interchange. And the entire effect of a depression in any single
large trade requires a considerable time before it can be produced.
It has to be propagated, and to be returned through a variety of
industries, before it is complete. Short depressions, in
consequence, have scarcely any discernible consequences; they are
over before we think of their effects. It is only in the case of
continuous and considerable depressions that the cause is in action
long enough to produce discernible effects.

The most common, and by far the most important, case where the