UNITED STATES OF AMERICA 



5954 



UNITED STATES OF AMERICA 



Moreover, forest fires, started by accident, and 

 sometimes by carelessness or design, have prob- 

 ably destroyed as much timber as was ever 

 cut. Through these various means the area of 

 standing timber has been reduced until it 

 amounts to only a little more than one-fourth 

 of the total laud area, which is not much 

 greater than the proportion in Germany, which 

 has been peopled for many hundreds more 

 years. In recent years the rapid advance in 

 price of lumber has shown that a timber famine 

 is to be expected unless the remaining forests 

 are carefully safeguarded and other forests are 

 planted on land too rocky or too sandy for suc- 

 cessful use in agriculture. 



Experience in other countries has also shown 

 that forests can best be maintained as a perma- 

 nent investment by the state, since the indi- 

 vidual may not live long enough to see a forest 

 crop mature. For these reasons the United 

 States government has in recent years estab- 

 lished numerous forest reserves which are 

 handled on business principles, and several of 

 the states, notably New York and Pennsyl- 

 vania, are following this example. It is un- 

 doubtedly true that considerable land still 

 under forest may well be cleared for farming, 

 but there is still more land already cut over and 

 burned over which ought to be reforested, if 

 the United States is not to suffer acutely in the 

 near future for the lack of forest products. At 

 the present time the largest cut of timber is in 

 the South, although the state of Washington 

 exceeds any other single state in its output. 

 The South is also the principal source of tur- 

 pentine and rosin. 



Minerals. Modern civilization differs from 

 civilization in ancient times, or in China to-day, 

 in no respect more strikingly than in the 

 greater use which it makes of mineral resources. 

 In fact, if civilization were deprived of miner- 

 als, all modern manufactures would become im- 

 possible, and so would modern methods of 

 transportation. In all ages important mineral 

 deposits have attracted population, but at no 

 time has this attraction been more in evidence 

 than to-day. Butte, Montana, built over a 

 great copper deposit, and Johannesburg, South 

 Africa, a city built on gold, are typical exam- 

 ples. From the sea, the forest, the farm and 

 the mine are derived all the materials used in 

 the most complex industries everything, in 

 fact, of a material sort which can help to satisfy 

 the needs of men. Of these several sources of 

 materials, the mine is second in importance 

 only to the soil. 



The United States is exceptionally well en- 

 dowed not only in respect to soil but also as 

 to mineral resources. These are found not 

 only in the two great highland areas and in the 

 lesser highlands in the interior plain, but also 

 in portions of the plains themselves. 



Structural Materials. The most widely used 

 minerals are structural materials, employed for 

 building purposes. Stone of various kinds was 

 no doubt the first mineral resource, and is still 

 one of the most important. Originally em- 

 ployed for tools and weapons, it now serves 

 chiefly for buildings and surfacing highways. 

 Granite, the most endurable stone, is quarried 

 in many localities throughout the United States 

 (see QUARRY AND QUARRYING, subhead Extent 

 of the Industry). Another stone which takes a 

 high polish is marble, formed from limestone 

 by heat and pressure during the upheaval of 

 the mountain ranges. Next to Vermont, Geor- 

 gia and Tennessee have the largest output of 

 marble. Other kinds of stone of commercial 

 importance are trap rock, of volcanic origin; 

 limestone and sandstone, both formed orig- 

 inally under water; and slate, a sedimentary 

 rock transformed by great heat and pressure. 

 Measured by value of product, indeed, lime- 

 stone and sandstone far exceed in value both 

 granite and marble, since they are quarried in 

 the plains as well as in the mountains and are 

 used more extensively for ordinary purposes. 



Limestone is also necessary in the smelting 

 of iron ore and the manufacture of concrete, 

 which is employed in building bridges, tunnels, 

 etc. The largest production of limestone is in 

 Pennsylvania, Indiana and Ohio, while New 

 York, Pennsylvania and Ohio lead in sandstone 

 (see page 4886). Slate is quarried chiefly in 

 the Appalachian Mountains, especially in Penn- 

 sylvania and Vermont. 



Fertilizers. Another important class of min- 

 erals comprises fertilizing materials. Experience 

 shows that three chemical elements tend to be- 

 come exhausted in soil long under cultivation, 

 namely, nitrogen, phosphorus and potassium, 

 yet these elements are absolutely necessary to 

 crop production. In the United States no de- 

 posits containing these elements have been 

 found in usable quantities, except in the case 

 of phosphorus. In the South, extending from 

 Tennessee through the Carolinas into Florida, 

 are vast prehistoric bone beds, probably the re- 

 mains of marine animals ; these yield phosphate 

 of lime, which is of great value in renewing 

 worn-out soil. Salt, associated in places with 

 gypsum and marking the margin of a former 



