10 INTRODUCTION
together for two months, and then undertook independent expeditions, Mr. Barrett going east from Khotan to China Proper, while I went east by another route to Lop-Nor, and then, turning north, arrived at Turfan in March, 1906, and reached home the following May via Siberia and Russia.
The journey through Chinese Turkestan from India to Siberia forms the main theme of this book, but I shall devote a few chapters to other parts of Central Asia. This volume, like the majority of so-called " geographical " books, is a description of a journey; but, as I have already said, it is also an attempt to describe certain parts of Asia as illustrations of the great principles of geography. My conception of that science, as stated above, is the one which has been spread abroad in the world at large, and especially in America, during the last few years by the persistent labors of Professor Davis. According to his definition, geography is primarily the study of the various natural divisions or provinces of the earth's surface as illustrations of the relations between the inorganic physical facts of the earth, air, and water on the one hand, and the organic facts of the vegetable, animal, and human world on the other. To illustrate : The investigation of the structure, origin, form, and climate of a lofty plateau and a neighboring arid plain is not geography, but geology, physiography, or meteorology. Neither can the study of the methods of plant growth and animal nutrition rightly be called geography, but botany or zoölogy. When, however, we consider the fact that because of the elevation of the plateau its climate is such that grass grows abundantly in summer; while the plain, being
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