Who can tell what the world may have lost by the early death of many a man of genius? One peculiar line of discovery which at first seemed to have nothing to do with practice has proved to be of signal service; the working out of mathematical methods of calculation by means of which the mechanical and physical sciences have in recent times made a progress in their practical application undreamt of by those who laid the foundations of geometry and algebra many centuries ago. It may, indeed, be said that all the sciences need one another, and that none has been without its utilities for practice, since even that which deals with the heavenly bodies has been used for the computation of time, was used by the agriculturist before he had any calendars to guide him, and has been of supreme value to the navigator. It has also been suggested that an observation of sun spots may enable the advent of specially hot seasons, involving droughts, to be predicted. Another kind of knowledge also grows by the joint efforts of many peoples, that which records the condition of men in the past and the present, including history, economics, statistics, and the other so-called social sciences. This kind also is useful for practice, and has led to improvements by which nearly all nations have profited, such as an undebased currency, banking and insurance, better systems of taxation, corporations, and joint stock companies. With this we may couple the invention of improved political institutions. The accumulation of knowledge, especially of scientific knowledge applied to the exploitation of the resources of Nature, means the accumulation of wealth--that is to say, of all the things which men need or use. The total wealth of the world must have at least quadrupled or quintupled within the last hundred years. Nearly all of it is in the hands or under the control of the civilised nations of European stock, among whom the United States stands foremost, both in rate of economic growth and in the absolute quantity of values possessed. [Sidenote: Knowledge Means Wealth]