The capitalist, therefore, can sell B for $1200, and make something over the current rate of profit. Since the cost of capital invariably resolves itself into these three variables, every capitalist in order to become successful as such must give strict attention to all three of these points. To any one who projects the making of valueless into valuable land, or valuable into more valuable land, by the expenditure of capital upon them for that purpose, it becomes a matter of prime importance for him to inquire how long a time the whole process will take, how much he must allow _per annum_ for the cost of all the implements employed, and especially how complete in action and duration are these costly implements. The _durability of machinery_, whatever the name it bear and whatsoever the work it do, is at once the most significant and the most neglected point in the actual and prospective Production of our time and country; and no condemnation can be too severe upon a policy of public law, such as now prevails, whose whole tendency and actual effect is to worsen the quality and lessen the durability of all commercial implements whatsoever, from the needle to the locomotive. The same abominable public policy increases the cost and decreases the durability of all agricultural implements, like the axe and the plough, designed and adapted to transform valueless and non-productive into valuable and food-producing lands. _2._ Now, having fully seen the elements of the cost of reducing land itself from a natural into a valuable and productive form, what next are the elements of the cost of production of those material commodities produced for sale _by the aid_ of these subdued and now productive lands? Commodities so produced constitute the second class in the law of their Cost of Production. And a vastly important class it is. The food of the world, so far as that food is purchased as the product, whether animal or vegetable, of valuable lands; the fuel of the world, so far as that fuel is bought from owned and accessible forests and mines; the clothing of the world, so far as the fabrics come from the cultivated cotton and flax and wool and skins offered for sale; the shelter of the world, so far as the wood and brick and stones and lime are drawn from valuable lands and quarries; and the warehouses and the temples and the theatres of the world, built, as they are, out of the products of costly and rentful lands: these all, and many more like these, constitute a class of commodities immense in their volume, whose cost of production has in it an element peculiar and additional to that of the first class already analyzed, and to that of the third class also soon to be considered.