Two further observations belong to this part of the subject. One is that this stock of useful knowledge, the accumulation of which is the central fact of the material progress as well as of the intellectual history of mankind, now belongs to (practically) all races and states alike. Some, as we shall note presently, are more able to use it than others, but all have access to it. This is a new fact. It is true that most races have contributed something to the common stock; and that even among the civilised peoples, no one or two or three (except possibly the Greeks as respects ancient times) can claim to have contributed much more than the others. But in earlier ages there were peoples or groups of peoples who were for a time the sole possessors of inventions which gave them great advantages, especially for war. Superior weapons as well as superior drill enabled Alexander the Great, and afterward the Romans, to conquer most of the civilised world. Horses and firearms, with courage and discipline, enabled two Spanish adventurers to seize two ancient American empires with very scanty forces, as they enabled a handful of Dutch Boers to overcome the hosts of Mosilikatze and Dingaan. So there were formerly industrial arts known to or practised by a few peoples only. But now all inventions, even those relating to war, are available even to the more backward races, if they can learn how to use them or can hire white men to do so for them. The facilities of communication are so great, the means of publicity so abundant, that everything becomes speedily known everywhere. [Sidenote: Inventions are now Universal] The other observation is that there is now no risk that any valuable piece of knowledge will be lost. Every public event that happens, as well as every fact of scientific consequence, is put on record, and that not on a single stone or in a few manuscripts, but in books, of which so many copies exist that even the perishable nature of the material will not involve the loss of the contents, since, if these contents are valuable, they will be transferred to and issued in other books, and so _ad infinitum_. Thus every process of manufacture is known to so many persons that while it continues to be serviceable it is sure to be familiar and transmitted from generation to generation by practice as well as by description. We must imagine a world totally different from the world we know in order to imagine the possibility of any diminution, indeed of any discontinuance of the increase, of this stock of knowledge which the world has been acquiring, and which is not only knowledge but potential wealth.