Synopsis Asia is the largest and most populous of the continents, but not the most densely populated, in which respect, like all the other continents, it has to yield pride of place to Europe. No exact comparison is possible between Europe and Asia, because there is no hard and fast boundary between them; they merge in the Soviet Union, which constitutes more than half of Europe and more than a third of Asia. If the dividing line between the continents be taken as following broadly the course of the Ural Mountains from north to south and thence the Ural River to the Caspian Sea, Asia may be assigned an area of 16.5 m. square miles and Europe 4.3 m.  square miles, with respective populations at the half-century of about 1.300 m. (more than half the world total) and 550 m. On the basis the average density of population in Asia per square mile is nearly 80 against nearly 130 in Europe. In Asia, especially, the population is very unequally distributed- extremely sparse in the north, centre, and south-west, while round the south and Cast coasts are some of the most densely populated areas in the world.