But so long as a people live unto themselves only, each nation can practically make and use all the machinery needed within its borders, and still not employ all the idle hands; and when the population becomes dense, employment must be sought in making goods to sell beyond the sea.

The return comes back, sometimes in money, sometimes in the products of the soil and the mine and the manufactures of foreign lands.
In this way every nation becomes like a great business firm.

It exports (that is, sells,) certain things, and it imports (that is, buys,) certain things; and if it sells more than it buys it is making money; if it buys more than it sells it is spending money.
This is usually expressed by saying that the "balance of trade" is in its favor or against it.
In a country like the United States, or any other great nation, the amount of exporting and importing, of buying and selling almost every conceivable article under the sun, is carried on in the millions and millions of dollars; and so perfect has the organization for doing this business become in every great country, that the products of the most distant countries can be bought in almost every village; and any important event in any country produces a perceptible effect wherever the mail and telegraph go.
The organization for effecting this in every country is so excellent and so wonderful, that it is like a machine.
In fact, it is a machine, and with all the faults of a machine.
Now one of the faults of a machine, a fault which increases in importance with the complexity of the machine, is the enormous disturbance which may be produced by a cause seemingly trivial.
That such is the case with the machine which the commerce of every great nation comprises, every-day experience confirms.

So long as the steamers come and go with scheduled regularity, so long will the money come in at the proper intervals and be distributed through the various channels; so long will the people live the lives to which they are habituated; so long will order reign.
But suppose the coming and going of all the steamers were suddenly stopped by a blockade.

While it may be true that, in a country like the United States, no foreign trade is really necessary; while it may be true that the people of the United States would be just as happy, though not so rich, if they had no foreign trade--yet the sudden stoppage of foreign trade would not bring about a condition such as would have existed if we had never had any foreign trade, but would bring about a chaotic condition which cannot fitly be described by a feebler word than "horrible." The whole machinery of every-day life would be disabled.