Another advantage of trade is, that industrious people in one part of the country, may supply customers in another, though distant. They may establish themselves in the most commodious places for their respective business, and help one another reciprocally, without making the distant parts of the country suffer for want of their labour. They are likewise exposed to no avocation from their work, by seeking for customers. Trade produces many excellent advantages; it marks out to the manufacturers when their branch is under or overstocked with hands. If it is understocked, they will find more demand than they can answer: if it is overstocked, the sale will be slow. Intelligent men, in every profession, will easily discover when these appearances are accidental, and when they proceed from the real principles of trade; which are here the object of our inquiry. Posts, and correspondence by letters, are a consequence of trade, by the means of which merchants are regularly informed of every augmentation or diminution of industry in every branch, in every part of the country. From this knowledge they regulate the prices they offer; and as they are many, they serve as a check upon one another, from the principles of competition which we shall hereafter examine. From the current prices the manufacturers are as well informed as if they kept the correspondence themselves: the statesman feels perfectly where hands are wanting, and young people destined to industry, obey, in a manner, the call of the public, and fall naturally in to supply the demand. Two great assistances to merchants, especially in the infancy of trade, are public markets for collecting the work of small dealers, and large undertakings in the manufacturing way by private hands. By these means the merchants come at the knowledge of the quantity of work in the market, as on the other hand the manufacturers learn, by the sale of the goods, the extent of the demand for them. These two things being justly known, the price of goods is easily fixt, as we shall presently see. Public sales serve to correct the small inconveniencies which proceed from the operations of trade. A set of manufacturers got all together into one town, and entirely taken up with their industry, are thereby as well informed of the rate of the market as if every one of them carried thither his work, and upon the arrival of the merchant, who readily takes it off their hands, he has not the least advantage over them from his knowledge of the state of demand. This man both buys and sells in what is called wholesale (that is by large parcels) and from him retailers purchase, who distribute the goods to every consumer throughout the country. These last buy from wholesale merchants in every branch, that proportion of every kind of merchandize which is suitable to the demand of their borough, city, or province.