It is to the astronomers and, glued to their telescopes or buried in their complex calculations, to whom we must go for knowledge of the magnitude of the earth, of ways of locating points, of reasons for climatic conditions, and day and night. And so geography, as a science, is related to their subjects. Probably the plains of Chaldæa and Babylon were the primal seats of observative astronomy. For there the unbroken plains of Mesopotamia could not arouse enthusiasm, but the phenomena in the heavens, changing with the days and the seasons, would most assuredly attract attention. Besides, the level expanses and the clear atmosphere gave excellent opportunities for observation. In the matter of map making, the basis for an understanding of distribution finds its foundation in a knowledge of latitude and longitude. Therefore the geographer is indebted to the mathematical astronomer for the graphical representation of the earth. We can not understand the make up of the earth, the so-called "mineral kingdom," unless we deal with chemical materials. It is the laws of physics which enable us to theorize about and understand the workings of many geologic processes, as mountain formation and volcanic activity. It is indeed obvious that physical geography rests in an intimate relation with these sciences; so much so, that certain phases of that study are termed geophysics and geochemistry.
In botanical fields such questions as these "What determines the flora of the steppes?" "Why are some regions treeless and others grassy?" "How is it that the same alpine plants are found on widely separated mountains and not in the intermediate area?" "Why is the cactus provided with water storage organs?" "What are xerophytes, hydrophytes, mesophytes?" These and infinitely many more questions of a similar nature will find their adequate answers only when based upon a knowledge of physical conditions and climatic facts.
In the study of animal life we do not find so direct a dependence upon geographic conditions as in that of plants, just as among men of to-day the dependence upon immediate environment is less marked than in the life of their primitive ancestors, largely because of the "power of locomotion." However, the mere existence of zoogeographical maps shows that there is, nevertheless, a distinct and important relationship. One finds that species and their distribution are determined largely by food, climate and physical conditions. The mountain goat, the camel of the desert, the river beaver, the wading and swimming birds, the antelope of the plains, the apes of the jungle, the reindeer and polar bear in the arctic, the coral in the warm seas—many of their adaptations are determined by the geography of their homes.
In the study of the highest of animals the same influence is of remarkable importance in the shaping of his character and habits. Why does the African have as occupations, hunting, fishing and modest kinds