The division of labor, as all writers on the subject have remarked, is limited by the extent of the market. If, by the separation of pin-making into ten distinct employments, forty-eight thousand pins can be made in a day, this separation will only be advisable if the number of accessible consumers is such as to require, every day, something like forty-eight thousand pins. If there is only a demand for twenty-four thousand, the division of labor can only be advantageously carried to the extent which will every day produce that smaller number. The increase of the general riches of the world, when accompanied with freedom of commercial intercourse, improvements in navigation, and inland communication by roads, canals, or railways, tends to give increased productiveness to the labor of every nation in particular, by enabling each locality to supply with its special products so much larger a market that a great extension of the division of labor in their production is an ordinary consequence. The division of labor is also limited, in many cases, by the nature of the employment. Agriculture, for example, is not susceptible of so great a division of occupations as many branches of manufactures, because its different operations can not possibly be simultaneous. (5.) “In the examples given above the advantage obtained was derived from the mere fact of the separation of employments, altogether independently of the mode in which the separated employments were distributed among the _persons_ carrying them on, as well as of the _places_ in which they were conducted. But a further gain arises when the employments are of a kind which, in order to their effective performance, call for special capacities in the workman, or special natural resources in the scene of operation. There would be a manifest waste of special power in compelling to a mere mechanical or routine pursuit a man who is fitted to excel in a professional career; and similarly, if a branch of industry were established on some site which offered greater facilities to an industry of another sort, a waste, analogous in character, would be incurred. In a word, while a great number of the occupations in which men engage are such as, with proper preparation for them, might equally well be carried on by any of those engaged in them, or in any of the localities in which they are respectively established, there are others which demand for their effective performance special personal qualifications and special local conditions; and the general effectiveness of productive industry will, other things being equal, be proportioned to the completeness with which the adaptation is accomplished between occupation on the one hand and individuals and localities on the other.”(118) § 4. Production on a Large and Production on a Small Scale.