For the comprehension of mathematical geography, a knowledge of the elements of mathematics and astronomy is indispensable. For determining localities, and for using many needed instruments, there must be some skill in practical astronomy; for measuring distances, for projecting maps and charts, and locating geographical districts upon them, there must be some familiarity with trigonometry and the higher mathematics. No one can thoroughly study geography in foreign lands, and leave all astronomical instruments behind. Political geography demands an acquaintance with history, and the same helps which the study of history requires. The civil status of no country can be determined without this. Büsching’s “Europe” was a master-piece of its time. But it was impossible for even that book to compress within its covers the whole history of that continent in its relation to the geography of Europe. The study of Man is, of course, in most intimate alliance with geography. It is only since the opening of this century that ethnography has become a prominent and clearly defined province of science, and enabled to become a great tributary of geography; in fact, the greatest tributary. Other departments are also drawn upon; there can be no close study of the soil, the structure of mountains and plains, without mineralogy and geology. Meteorology, too, the science which discusses the climatic conditions of countries and the effects of climate upon the organization of plants, animals, and man, is of no mean value in illustrating geography. Nor can one be a great geographer who does not understand the flora of the world. Not that he needs to be familiar with the myriads of plants, but the laws of growth and the characteristics of localization must be known. The geographer does not need to repeat in detail where the cereals and the palm-tree thrive. The general conditions which control the growth of plants are all that he has to concern himself with. The main auxiliary for this is furnished in the botanical garden, where the eye sees the products of all localities, arranged, according to their grouping, in the countries where they are indigenous. Botany and zoology and mineralogy are among the sciences most valuable in throwing light upon geography; they display best what wealth each country holds in store for the uses of man; for they are closely connected with the development of industry, the arts, and trade.