2. _Discovery of new lands and of new natural deposits continually enlarges the economic supply of the agents most nearly fixed in physical amount._ This proposition states a historical fact. Any explanation of the economic occurrences of the last five centuries or of the immediate future, that ignores this fact of the increasing supply of many kinds of land and natural resources in the markets of the civilized world, must lead to false conclusions. The rate of this movement has been more rapid in the past century than theretofore, and perhaps more rapid than it will be henceforward; but that this development will continue in large measure and for a long period, is not open to question. Undeveloped areas will be opened to the world, and new geologic realms will be explored. Yet the notion criticized above is found in all the older text-books. The idea arose in England in the first quarter of the nineteenth century when land and food were rapidly rising in price, and it has vitiated a large part of both the economic theory and the practical conclusions on this subject. [Sidenote: The effective supply grows by invention] 3. _Invention, including new modes of transportation and new processes, increases the economic supply of most scarce goods and provides substitutes for the others._ Some inventions increase economic supply by making available the uses in goods that were before unavailable. Subsoil ploughing annexes to agricultural land new layers of soil that are just as important as new acres added to the surface. If land could be used three times as deep, it would be as good for many purposes as if it were of three times the extent. New trade routes and new means of transportation add to the supplies available in the older countries as effectively as if their areas were increased. The building of railroads in western America had an effect on English rents identical in nature with that which would have been produced had an equal area of somewhat less fertile land touching England, risen out of the ocean. Every country in Europe has repeatedly felt the shock of these great economic changes which have compelled the recapitalization on a lower plane, of nearly all kinds of their landed wealth. Where the same agents have not been multiplied, substitutes have been found that are just as effective in meeting the economic need. It is the result, the gratification, that man seeks: any particular good is but the means to an end. [Sidenote: Production of land by physical change]