But to give additional durability to the instrument there must be additional labor bestowed on its formation.An increase of the durability of an instrument may therefore be considered as a power communicated to it of giving existence to a new instrument at the end of a certain period, and purchased by a present expenditure.The effects produced by the change will be determined by the relations subsisting between the returns made by the addition, its cost, and the time elapsing between the expenditure and return.If we suppose the present expenditure necessary to produce the durability, to be always equal to the durability produced, then the compound instrument will be moved towards the more slowly returning orders, because the new instrument is in that ease one of slower return.One dwelling-house lasts thirty years;another, the same as it in other respects, but costing double the expense of formation, lasts sixty years; the former house is an instrument of the order O, doubling in fifteen years.The part of the duration of the latter extending from the thirtieth to the sixtieth year, is to be considered, by our hypothesis, as a separate instrument.If we suppose, that during the time it is in use it returns as the other, at the end of the sixtieth year it will have returned only four, and, therefore, is an instrument of the order C doubling only in thirty years.The compound instrument will, in consequence, be of an order between X and Y, doubling in between twenty-four and twenty-five years.The procedure of adding to the durability, by adding equally to the expense of formation, will have greater effect in placing an instrument further from A, the more it is subjected to its operation.
Thus, were an instrument of this sort to have its duration prolonged to one hundred and twenty years, and at the same expense, the last thirty would return only four in one hundred and twenty years, whereas, had it formed an instrument of the order O, it ought to have yielded two hundred and fifty-six.Were the durability increased still farther, at the same cost, the divergence would be much greater, going on in a geometrical ratio.
If, therefore, continual additions be made to the durability of an instrument, it cannot be preserved at an order of equally quick return, unless the several augmentations be communicated to it, by an expenditure diminishing in a geometrical ratio; that is, in a ratio becoming indefinitely less, as it is continued.This, however, cannot happen, for, it would imply an absurdity.While instruments are in existence, they are either producing events, or giving a new direction to their course.But, mere matter, unless in some very rare instances, is never acting, or acted upon, without undergoing a change.This we term wear, and the effects it indicates form consequently a definite power, to counteract which, a definite force must be found.
It cannot then, be counteracted, by a force indefinitely small.
The same thing may be illustrated in another manner.When events are produced and governed by design, they in turn generate other events of greater powers than themselves, and these others, in a series rapidly increasing.
Mere durability in instruments, may be considered as a capacity to generate future events, lying dormant in them, till the lapse of years exposes its existence, and gives it opportunity to act.The greater the time therefore, for the expiration of which it must wait, the less the chance of its being on an equality with rivals, whose powers are continually and rapidly multiplying either events, or enjoyments, whenever they have a field on which to exert their energies.
While the knowledge of the course of events which the members of any society possess remains unaltered, and the materials they own are the same, the duration of the instruments they form cannot, consequently, be indefinitely increased, without their being moved, farther and farther, from the more quickly returning orders.
The durability of instruments refers only to those of gradual exhaustion;their efficiency, or the extent of their power to bring about events within a certain time, refers both to those of gradual, and of sudden exhaustion.
If the knowledge of the course of events, and the amount of the materials remain the same, the efficiency of these materials when formed into instruments cannot be indefinitely increased, without that increase being at length made with additional difficulty, and through means of an amount of labor greater than was required in the earlier stages.The action of matter upon matter always depends on some cause.Those causes, -- the inherent qualities and powers of the different matters around him, -- are the means man employs to make one material to act so on another as to produce the events he desires, and he does so by applying his labor to give them such a form and position as may bring their powers into play.If we suppose any number of men to be fixed to one situation, and their knowledge of the qualifies of the materials around them to remain stationary, they will naturally first make choice of those materials, whose powers are most easily brought into action, and which produce the desired events most abundantly and speedily.But as the stock of materials which any society possesses, is limited, its members, if we suppose them to acquire no additional knowledge of the powers of those materials, and yet to add continually to the amount of instruments they form out of them, must at length have recourse to such as are either operated on with greater difficulty, or bring about desired events more sparingly or tardily.The efficiency of the instruments produced must therefore be generated by greater cost; that is, they must pass to orders of slower return.
