lubricated grooves, cylinders, and sockets through which the parts of a machine are made to move. Roads, streets, and railway tracks will be discussed under the head of transportation. The rest must be left to the imagination of the student.

Noneconomic properties of land. Some of the physical and geometric properties of land which are the most fundamental are not the most important from an economic point of view. The solidity of the earth which serves to support our weight, and that of the buildings which we erect and the plants which we grow, is of course essential to our very existence. It is not a matter of the greatest economic interest, however, because it is not so scarce as some other properties. Rocky or desert land, of which there is an abundance, furnishes support as well as fertile land. The quality of extension, that is, superficial area, is also essential. It is this which enables us to catch and utilize the sun's rays, the rain, and the dew. It is this which provides room for plants to grow, to spread their roots to the soil and their leaves to the air. It is this which furnishes space for the erection of buildings and the carrying on of all activities. This quality of extension, however, is possessed by sterile as well as by fertile land, and by land which is badly located as well as by land which is well located.

Economic properties. Location may also be said to be a geometric property of land. It is a matter of great economic importance, because there is such a scarcity of land in the best locations. By location is meant proximity and convenience of access to markets, roads, schools, scenery, and various other desirable things. Some land is greatly superior to other land

in this respect, and this creates a great difference in the desirability of different lands. Location is the chief, almost the only factor in determining the value of urban land. In a place where multitudes of people desire to live, land is necessarily scarce, but the scarcity is a scarcity of land well located for urban purposes; that is, for business or for the dwellings of those who have to live within reach of the business establishments. Moreover, the differences in the value of lands within a city are due almost wholly to differences in location. In agricultural communities location is a factor, but not the only nor the most important factor, in determining land values. Nearness to market or to railroads, the character of the wagon roads, accessibility to schools and other social advantages, count for much; but the character of the soil and the subsoil, the climate, the moisture, and the other factors which determine plant growth, count far more. All these factors which promote plant growth may be grouped under the name fertility. In that case we may say that from an economic point of view location and fertility are the most important properties of agricultural land.

Good location saves transportation. When we look for the reason why location is a matter of such importance, we must recall the fact that man's chief work, on the physical side, is the moving of materials. It is this which requires power; and power is costly, whether it be generated in the human body and exercised through the muscles, or whether it be developed in the bodies of animals, or through mechanical agents. One very important phase of the work of moving materials is that of marketing products. The nearer a body of land is to a market, and the better the means of transportation, the less labor and power it takes to get its products to market. On land which is well located with respect to markets it is therefore possible to utilize labor more efficiently than on land which is badly located. It is also costly to move man himself. It is therefore advantageous that he should live in close proximity to his work.

If he lives far away, the cost of transportation is greater, and the labor force of the community is less efficiently applied, than if he lives close by. Even though the trolley fare is the same for a long as for a short distance, transportation costs more over the long distance. In the first place, it takes a longer time and the passenger loses that time. In the second place, it costs the transportation company more, and that extra cost must ultimately reduce the total productive power of the community. The extra labor required to transport passengers a longer distance might otherwise be used in other lines of production. However, the sheer scarcity of land, both for business and for residence purposes, forces population to spread and makes longdistance transportation necessary, however costly it may be.

In proportion as transportation can be cheapened, in that proportion will questions of location become of less importance from the standpoint of production. From the standpoint of consumption or direct enjoyment, cheapened transportation would apparently make little difference. Certain neighborhoods, because of neighbors, scenery, fashion, and a variety of reasons, would still be preferred to others. If one could imagine costless transportation, such as is pictured in the Arabian Nights by the story of the magic rug, on which one could be instantly transported to any distance, one location would be as desirable for production as another; that is to say, if there were no difference between two pieces of land in fertility or in anything else except location, they would be equally desirable. It would cost no more to transport products to market, or men to and from their work, in one case than in another. So far as location is concerned there would be no scarcity of land until all the unoccupied portions of the earth were occupied and utilized. In short, such a perfect system of transportation would vastly increase our available supply of usable land.

While it is obvious that no such instantaneous and costless system of transportation will ever be devised, it is equally obvious that the more nearly we can approach that system the

more land we shall have available for all sorts of purposes. It is the superiority of modern as compared with earlier means of transportation which makes possible those vast aggregations of people known as cities. They can draw their supplies from greater distances and in greater abundance than would be possible with less efficient means of transportation. Ancient cities that were situated on navigable rivers or on the seashore had the advantage of water transportation, which, even before the days of steamships, was fairly cheap and efficient. Nonperishable products, such as wheat, could then and can still be transported long distances in sailing vessels at low cost. Consequently, where water transportation was possible, cities of considerable size grew up long before the days of steam railways. But inland cities, such as many of those which dot the maps of every progressive country, would have been an impossibility.

Access to food supplies. It seems to be a general rule, applying to all forms of life, that numbers depend upon food supply. Where food is abundant, numbers may be large. Since food comes ultimately from the soil, the capacity of the soil to produce food places a limit upon numbers. One of two things must, of course, follow: a large population must either spread over wide areas of land in order to find sufficient food, or it must transport food from these wide areas where it is produced to the densely populated centers where the people live. Certain birds reverse this process and manage to live a part of the time in large flocks and transport themselves to and from their feeding grounds. If they are strong fliers, as were the wild pigeons which formerly inhabited this continent, they may feed over large areas and return to their roosting places at night. It was their remarkable powers of flight which enabled such vast numbers to roost in the same locality; otherwise they would have been compelled to break up into smaller flocks in order to live nearer their feeding grounds. The same law. seems to apply to human flocks. If we were not able to transport food and other supplies such long distances, our large