And there is a partnership in industries.  No single large industry can be depressed without injury to other industries; still less can any great group of industries.  Each industry when prosperous buys and consumes the produce probably of most (certainly of very many) 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 depression in one trade causes depression in all others, is that of depressed agriculture.  When the agriculture of the world is ill off, food is dear.  And as the amount of absolute necessaries which a people consumes cannot be much diminished, the additional amount which has to be spent on them is so much subtracted from what used to be spent on other things.  All the industries, A, B, C, D, up to Z, are somewhat affected by an augmentation in the price of corn, and the most affected are the large ones, which produce the objects in ordinary times most consumed by the working classes.  The clothing trades feel the difference at once, and in this country the liquor trade (a great source of English revenue) feels it almost equally soon.  Especially when for two or three years harvests have been bad, and corn has long been dear, every industry is impoverished, and almost every one, by becoming poorer, makes every other poorer too.  All trades are slack from diminished custom, and the consequence is a vast stagnant capital, much idle labour, and a greatly retarded production.