第42章

Since then man provides a supply for his future wants by his reason directing his industry, through means of his knowledge of the course of.events, to effect such changes in the form or arrangement of the parts of material objects, that these may produce articles fitted to afford this supply, it were desirable to have some common name to denote all the changes, which, for this purpose, he so makes.On this account I propose to give the denomination of instruments to all those changes that, for this purpose are made in the form or arrangement of the parts of material objects.

The term instrument is, in general, properly enough employed, to denote any means for the attainment of some end.In common use, however, and as applied to material things, it seems to be restricted to such arrangements of matter as owe their chief efficacy to what are called the mechanic powers.

Thus a lever or a wedge is an instrument, the manner in which each of them operate being chiefly explained on mathematical principles.A spade, which is a combination of the two, is also an instrument.The tools which carpenters use are instruments.We speak in the same way of instruments of husbandry, meaning by the phrase the articles used in that art, whose properties may be explained on mechanical principles.

In all these cases, however, other principles than those which are merely mathematical must enter into our calculations.In the simplest-lever, we have not only the properties of a mathematical line to consider, but also, the weight and strength of the substance used, and these make the difficulty in the proper application of such an instrument.A wedge operates in many ways, besides those that may be considered to be derived simply from mathematical principles; as for instance in the percussion, which it receives and communicates, and through means of which, if skilfully applied, the most solid rocks may be rent.The farther we recede from such simple instruments, the more extensive do we find the action of properties, which could only be ascertained by a long series of observations.It would be impossible, for instance, to give any a priori rules for the construction of that most useful instrument the plough.It is, no doubt, a wedge, but the particular form giving the greatest efficacy to it, is a point of very difficult determination, not yet, perhaps, fully ascertained.It is accurate observation that has guided the construction of it, to its present efficiency, and which may be expected to render it still more perfect.

Were we to enter into an examination of more complicated machines or instruments, such as the steam engine, or the cotton mill, the observation would apply with double force, these generally deriving their efficiency from principles, that have been the result of very extensive and accurate investigations of many series of events.In thus using the term, therefore, we shall rather deviate somewhat from common usage, than be opposed to it, and in doing so, our reasons will only be subject to an inconvenience, to which all general reasons must be subject, and which quay be the more readily excused, as this use of the term may be defended from its derivation, its occasional acceptation, and the authority of authors of respectability.(33)In general then, all those changes which man makes, in the form or arrangements of the parts of material objects, for the purpose of supplying his future wants, and which derive their power of doing this from his knowledge of the course of events, and the changes which his labor, guided by his reason, is hence enabled to make in the issue of these events, may be termed instruments.

In this sense a field is an instrument.The changes effected in the matters of which it is composed, for the purpose of rendering it an instrument, are the levelling and if necessary making the surface dry by means of ditches and drains, the removing stones from it, the mixing and pulverizing the soil by the plough, the harrow, and the roller, and the incorporating with it various matters termed manures, which render it more fit for the support of vegetable life.The future wants, towards the supply of which it is an instrument, are food and clothing.The power which has made it an instrument, is the agriculturist's labor, directed by his knowledge of the nature of plants and soils.The change made in the consequent issue of events, is the abundant growth of specieses of plants different from those originally produced by it, and conducing to the supply of food and clothing, or, more generally, the conversion of various vegetable matters of the soil, and gaseous matters in the air, into the substance of particular plants.The wheat grown on this field is an instrument.The changes effected in it, are its having been separated from the straw by the process of threshing, and its having been made sufficiently dry by keeping and exposure to air, to be fit to manufacture into flour.The want it tends to supply is nourishment, by affording bran for the support of some of the inferior animals, as hogs or cattle, afterwards to be slaughtered, and flour for the use of man.

The power is also the art and industry of the agriculturist.The change in the issue of events consists in the grain being ready for the manufacture of flour, instead of having been left to rot on the ground, to be consumed by vermin, or destroyed by the access of damp or by the want of air.Flour also is an instrument.The changes that have been effected on it are its having been separated from the wheat, and reduced to a fine powdery matter.

The want it tends to supply is food by the bread produced from it.The power, which has operated on it, is the art and industry of the miller.