ships by way of India and the Red Sea. In 66 B.C. Roman troops under Pompey followed in the footsteps of Alexander the Great, and marched up the eastern shores of the Caspian Sea. In 102 A.D. a Chinese expeditionary force under Pan Chau reached the Caspian, and sent emissaries to report upon the power of Rome. But many centuries were still to pass before definite knowledge and direct intercourse were to link the great parallel worlds of Europe and Eastern Asia.
To the north of both these great empires were barbaric wildernesses. What is now Germany was largely forest lands; the forests extended far into Russia and made a home for the gigantic aurochs, a bull of almost elephantine size. Then to the north of the great mountain masses of Asia stretched a band of deserts, steppes and then forests and frozen lands.
In the eastward lap of the elevated part of Asia was the great triangle of Manchuria. Large parts of these regions, stretching between South Russia and Turkestan into Manchuria, were and are regions of exceptional climatic insecurity.
Their rainfall has varied greatly in the course of a few centuries They are lands treacherous to man. For years they will carry pasture and sustain cultivation, and then will come an age of decline in humidity and a cycle of killing droughts.