There is a great wealth of literature about what we call the world's productive lands--that is, the densely peopled lands that yield grain, meat, sugar, fruit, and all the various foodstuffs. In any well-equipped library we may find great numbers of useful books that will tell us all about the places where cotton, wool, and silk are grown, or where coal and iron are mined. All these lands are the dwelling places of many people. Networks of railways connect the various cities and villages, and probably a majority of the people living in them have travelled in and about much of the area of these lands. A large part of the earth's surface is commonly called "unproductive." As a rule this is only another way of saying that such parts of the world produce little foodstuffs. We must not take the word "unproductive" either too literally or too seriously, however, for Dame Nature has a way of secreting some of her choice treasures in places so forbidding and so desolate that only the most resolute and daring men even search for them. For instance, the mineral once much used by the makers of carbonated or "soda" water comes from a part of Greenland that is so bleak, cold, and inhospitable that no human beings can long exist there unless food and fuel are brought them from afar off. The famous "nitrates" of Chile are obtained in the fiercest part of the Andean desert. Not only the food but the water consumed must be carried to the miners, who are but little better than slaves. Most of the gold and silver is obtained in regions that are unfit for human habitation. The largest diamond fields in the world are in a region that will not produce even grass without irrigation--a region that would not be inhabited were there no diamonds. From the most inhospitable highlands of Asia comes a very considerable part of the precious mineral, jade. Death Valley, in the southern part of the United States, on account of its terrific heat, is perhaps the most unhabitable region in the world, but the borax which it produces is used in every civilized country. And so we might name regions by the score that are practically unhabitable, which nevertheless produce things necessary to civilized man.