2. _Most of the qualities that contribute to make land fertile in agriculture being destructible, the constant repair of tilled land is necessary to its continued fertility._ If any things could be said to be indestructible, they would be some of the works of nature. In a sense, all matter is indestructible. Man cannot annihilate it, he can simply change its condition. But in economic discussion it is the value of things that is being considered, and from this point of view everything is in some degree destructible. The effects of bad husbandry are everywhere apparent, and in many regions fertile fields have been physically and economically destroyed. In Asia, lands that once supported millions, perhaps hundreds of millions, of population are now deserts. Egypt, for a time reduced to a semi-desert condition, has only in the past century been restored to a certain extent by the use of new methods and a return to the old ones. Many of the areas that were the granaries of Rome can now hardly support a sparse, half-starving population. The lands, or at any rate, the elements that gave them value, have been destroyed. [Sidenote: Wearing out of some American lands] Even in young America may be seen the effect of a failure to keep land in repair. As the new rich lands of the West were opened up, the old lands in the East were allowed to wear out, and many of them were abandoned. On the new lands in turn the same methods were followed, using up the first rich store of fertility with no attempt to keep up the quality of the soil. This may have been the best policy for the time; it would not have been economical to employ Old World methods of intensive husbandry when such rich extensive areas were being opened up. But the process was one destructive of natural resources. As settlement moved westward, great forests fell in ashes, and the soil was robbed of the fertile elements which it had taken centuries for nature to store up. [Sidenote: Wearing out of the parts the railroad] 3. _The machinery and appliances used in transportation and manufacturing are all perishable in varying degrees._ Take as an example the great agency for transportation, the railway. The roadbed, which is but the natural soil excavated or filled to a better grade, is the most permanent part; yet every frost weakens, every rain undermines, a portion of it. Earthquake, landslide, and flood fill up the ditches, or tear down the embankments. Constant work is needed to keep it fit and safe for use. Above this is the track, slightly less permanent, more frequently changed. The ties rot, and even the rails of steel must be at times replaced. The rolling-stock is still less durable, and the different parts vary in length of life. It is said that the wheel-tires are renewed four times, the boiler three times, and the paint seven times, before a locomotive is entirely worn out. The oil used in the wheel, which is a necessary part of the running machine, has to be applied every day.