As will appear from the study of the following pages, with the exception of some parts of central Europe or of some sporadic attempts elsewhere to regulate forest use, the development of the forestry idea belongs essentially to the 19th century, and more especially to the second half, when the rapid development of railroads had narrowed the world, and the remarkable development of industries and material civilization called for increased draft on forest resources. Yet we are still largely ignorant as to the extent of available forest area, not only in this country but elsewhere: we do not know whether it be sufficient in extent and yield to furnish a continuous supply for the needs of our civilization, or, if not, for how long a time it will suffice. We can only make very broad statements as to questions of wood supply, and very broad inferences from them as argument for the need of a closer study of forest conditions and of the practice of forestry: 1. Practically, the northern temperate zone alone produces the kinds of wood which enter most largely into our economy, namely the soft conifers and the medium hard woods; most of the woods of the tropics are very hard, fit primarily for ornamental use and hence less necessary. Possibly a change in the methods of the use of wood may also change the relative economic values, but at present the vast forests of the tropical countries are of relatively little importance in the discussion of wood supply for the world. 2. The productive forest area, of the temperate zone, in which the industrial nations are located, has continuously decreased. We shall not be far from wrong in stating this area liberally, to be at present around 2,500 million acres,[1] namely in Europe, 800 million acres; in Asia, 800 million acres; in North America, 900 million acres. How much of this acreage contains available virgin timber, how much is merely potential forest, how much growing crop, it is impossible to state. [1] The total forest area of the world is supposed to be 3,800 million acres. 3. The civilized wood consuming population of this territory is about 500 million, hence the per capita acreage is still 5 acres. Taking the European countries which now have to import all or part of their consumption (excess over exports), we find that their population is estimated at 180 million and that they use 30 cubic feet of wood per capita, of which 12 cubic feet is log timber; or altogether they use 2,200 million cubic feet of this latter description, of which they import in round numbers 1,000 million at a cost of about 250 million dollars; their forest acreage of 100 million acres being insufficient to produce, even under careful management as in Germany, more than two-thirds of their needs. And the wood consumption in all these nations is growing at the rate of 1½ to 2 per cent. annually.