Of the three great employments of national industry, that of giving to raw produce the forms adapted to the purposes of man, or of manufactures, requires the most manual adroitness. In this talent there is a great diversity among individuals, so that some are able to do as much in an hour as others can in twice or thrice the time, and not seldom perform operations to which most others are incompetent. There is, indeed, in every mechanical employment, as in the nicer productions of art, as great a difference in the goodness of the work, as in the celerity with which it has been produced. Hence, some acquire reputation as bootmakers, tailors, hatters, or as makers of fine cutlery, cabinet-work, watches, or jewelry. Even in the simple operations of making nails or bricks, the labor of some is twice as efficient as that of others.

But the greatest advantage possessed by manufactures in the employment of labor is, that they admit the co-operation of several individuals in the same object, by which the product is so greatly multiplied. This was first noticed by Adam Smith, under the designation of the "division of labor," and was strikingly illustrated by him in the manufacture of pins. If one person was to perform all the operations required for the fabrication of this little implement, he could not make twenty pins in a day - perhaps not more than one; but by distributing these several operations among a dozen or twenty workmen, the proportional number to each one would be upwards of 4000 pins in a day.

This prodigious gain is referred by Smith to three circumstances: the increased adroitness and rapidity of execution acquired in the performance of a single act; the saving of time which would be lost when a workman passes from one operation to another, which perchance is to be executed in another place, as well as with other tools; and lastly, machinery may be more extensively substituted for human labor in proportion as the operation is more simple.

The gain from the last-mentioned source may be illustrated by some striking examples. The machine which makes wool or cotton cards has saved an immense amount of human labor, that was previously expended in forming its little wire-hooks, one by one, and, by the same slow process, inserting them in a piece of leather perforated to receive each hook. At present, the machine cuts the wire to a proper length; bends it into a hook; perforates the leather - at the same time inserting the hook, until the card is complete. All this occupies so little time, that the card is then sold for a small part of what it had formerly cost.

But of all labor-saving machines, the cotton-gin, in a national point of view, is the most important. Before it was invented, the seed of that species of cotton which can alone be cultivated in the interior portion of the United States, was separated from the fibrous part by the human fingers; by which operation one person could clean not more than a pound a day. Thus furnished in such small quantity, it was valueless as an export, and was used only to a moderate extent for manufactures in the Southern States. But after Whitney's invention of the saw-gin - a combination of circular saws and brushes, the simplest moving-power - a small stream, or a horse, was made to perform this work at an insignificant expense, so as to render cotton a general article of culture, where the climate permitted its growth, until it became an export of more value than that of all other commodities combined.

The manufacture of cotton into cloth has received improvement as great as has the production of the raw material. The inventions which have been made in England for carding, spinning, and weaving cotton by machinery, have so facilitated the manufacture of this material, that they have contributed as much as the cotton-gin to the cheapness of its fabrics; and, by their joint operation, a large proportion of those fabrics now sell for one-sixth or one-eighth part of their former cost. All the operations of manufacturing cotton-cloth, which were once performed by human hands, are now done, and better done, by machines, which are put in motion by running water, or steam, or horses; and the consumption has been so extended by its cheapness, that it now gives profitable employment to a far greater number of persons than ever.

The machinery which has so lessened the cost of cotton fabrics has been also applied to those of wool and of linen, but not to the same extent, nor with the same advantage.

When, in political economy, labor is considered to be of uniform value, it refers only to labor in its simplest form - that of an ordinary man, exercised with ordinary skill. But in truth, there is no merchantable commodity which varies in value more than human labor; and it is proper to notice the sources of this diversity.

First. The difference of skill which an employment may require. The superiority may consist either in manual dexterity, as in the case of a mechanic, or in professional knowledge, as in the case of a lawyer or physician, or of both united, as in the case of a surgeon; and it is immaterial whether the skill be the result of previous instruction, or the endowment of nature.

In many branches of industry, the most toilsome portions of the labor expended are of the cheapest kind, while another portion, requiring extraordinary skill, finds its remuneration only in a very high price. Thus the first preparation of a piece of marble for a statue may be performed by an ordinary stone-cutter, at the low wages of common labor; but the last part of the process of making such intractable material closely copy the diversified forms of animal life may command twenty, or even fifty times as much remuneration. So of the finest piece of work in watchmaking, and the manufacture of plate or jewelry.

Secondly. The price of labor varies, also, according to the greater or less agreeableness of the operation. In the same degree that an employment is distasteful, its compensation must be higher, to counterbalance the disadvantage. Hence the office of an executioner, which is naturally revolting to the feelings, and is therefore held in great aversion or contempt, is commonly very well rewarded. This odium has probably suggested those machines which have been devised to execute the dread sentence of the law without the visible agency of man, as the maiden in Scotland, and the guillotine in France. The business of negro-trading is also one which is generally odious, as violating the dictates of humanity, and as implying a want of human sympathy. To compensate this unpopularity, the trade is very profitable. The great gains of the African slave trade long avowedly prevented its abolition by the British Government. Even now they are often sufficient to defy the hostility of the principal maritime powers of the world.