_b._ In no country are the coasts more indented. We may look in vain for such a sea-board as that of Greece, elsewhere. The effect of this is to give the different characters of the sailor and landsman, the producer and the trader, more opportunity of acting and reacting on each other. _c._ Its greatest rivers fall into seas navigable throughout the year. Contrast with this the great rivers of Asia, the Obi, the Lena, the Yenesey, and others, which for the purposes of navigation are useless; falling, as they do, into an Arctic sea. _d._ Our greatest river, the Danube, runs from east to west. This ensures a homogeneous character for the population along its banks. Contrast with this the Nile, the Missisippi, and the Yenesey, in all of which the simple effect of climate creates a difference between the populations of the source and the embouchure. The great rivers of China do the same as the Danube; but the Danube differs from them, and from all other rivers running in a like direction, in emptying itself into an inland sea; a sea which gives the opportunity of communication not only with the parts north and south of the rivers which fall into it, but with those to the east of it also. The Hoang-ho and Kiang-ku empty themselves into an ocean, that, in these days of steam communication, leads to America, but which in the infancy of the world led to a coasting trade only, or, at most, to a large island--Japan. The Baltic and Mediterranean act, to a certain degree, in the same manner. The one has Africa, the other Scandinavia, to ensure its being put to the uses of trade. In no part of the world do the differences between the varieties of the human species lie within narrower limits than in Europe. The most extreme opponents to the doctrine of the unity of our kind have never made many species out of the European specimens of the genus _Homo_. And these are by no means of the most satisfactory sort. They are unsatisfactory for the following reasons. The differences that are inferred from dissimilarity of language, are neutralised by an undoubted similarity of physical form. The dissimilarities that are inferred from peculiarities of physical form are neutralised by undeniable affinities of speech. Looking to his size and colour, the Laplander is far, very far, removed from the Fin. Yet the languages belong to one and the same class. Looking to their tongues, the Basque of the Pyrenees, and the Skipetar (or Albanian of Albania) are each isolated populations. Yet their form is but slightly different from those of the other Europeans. Now the physical condition of our continent makes the intermixture of blood, and the diffusion of ideas easy: and, I believe, that the effects of both are more notable in Europe than elsewhere. 2. The families, stocks, or races, which occupy Europe will be taken in the order which is most convenient; so that it will be practical rather than scientific.