It will be my effort, in the course of these lectures, to exhibit the subject of relations rather than to detain you with descriptions; in one word, to generalize rather than to add new details. In the lack of a thoroughly excellent text-book of geography, I shall presuppose an acquaintance on your part with the materials, so to speak, of which the science is to be constructed. It has been a customary method to treat geography in connection with epochs of time; dealing with it as it was in the past and as it is in the present. We hear of Ancient Geography, the Geography of the Middle Ages, and Modern Geography. In this course of lectures, it will be treated not as the property of one age or another, but rather as a growth of all time, from Herodotus down to our day. It is only in this way that we can ascertain what is permanent and what is ephemeral; only in this way can we subject geography to that comparative method which has given such an impetus to the advancement of the sister sciences of Natural History; only in this way can we see how the present is the birthright of the past. Archæology, ethnography, and civil science are all gainers by this method of treatment; in one word, the whole domain of cotemporaneous study. The less positive knowledge we possess of the formative processes of science, the more crude our hypotheses, the more flagrant our errors. This is constantly verified under our eyes; the errors of the past are the wisdom of the present, and the gradual upheavals of our knowledge become indices, not less of outgrown untruths than of truths yet to be revealed. SOURCES OF GEOGRAPHICAL SCIENCE.