_Effects of Reduced Cost of Materials which already enter into Many Finished Products._--In the case of aluminum the prospect of a greatly increased market brings with it the probability that it may come to be a component element of products into which it does not at present to a great extent enter. Such things as steel, stone, and wood already constitute important components of more articles than can be counted, and there is no great prospect that they will enter into a much greater variety of products. In the case of these materials there is a prospect that cheapness will show itself in reduced costs of the finished goods that are made of them, and that these finished goods will be used in greater quantities without substituting themselves for other things in so drastic a way as that which we have described in the case of aluminum. A reduction in the cost of steel would indeed bring about a substitution of that material for others at every point where the steel and something else are now on a plane in desirability. The type of building that now is made with plain brick walls and wooden floors, because that cheap mode of building enables it to earn a slightly larger interest on its cost, would often be made with a steel frame and concrete floors. At every such marginal point steel would gain somewhat on its rivals in the extent to which it would be used; but in addition to this enlargement of the market for it by substitution, one might count on an increase in the use of it because of an increase in the use of very many things that are already made of it. Some of these cater to highly elastic wants, and persons who use a quantity of them may be induced to use more without discarding anything else. Such an absolute enlargement of consumption is highly probable in the case of any material that enters into a vast number of products, and this, together with the enlargements that come by substitution, may suffice to create a great demand for the raw material and call for as much labor in the subgroup that makes it as was used before the improvement was made. In the case of the raw materials of industry the resources for gaining an increased market by substitution are:-- (1) The substitution of the material for others in uses different from those in which it is now employed; (2) The substitution of it for other materials in the marginal parts of its present field, where it is already nearly as available as other things; (3) The substitution of the finished consumers' goods made of it for other consumers' goods. In addition to all these there is the direct increase in the use of finished goods wholly or partly made of the material by persons who do not, for this reason, discard any other goods. This statement places the different influences in the order of their relative efficiency in the majority of cases in which they act.