in their turn, disclosed fresh tropical areas worth exploiting, and introduced new luxuries, such as tobacco and tea, which soon took rank as necessities.  They also brought a colossal increment of wealth to the countries which had undertaken them.  Hence the acquisition of a share in, or a monopoly of, these lucrative lines of trade became a primary object of ambition to all the great states.  In the nineteenth century Europe began to be unable to supply her own needs in regard to the products of the temperate zone, and therefore to desire control over other areas of this type; but until then it was mainly in regard to the tropical or sub-tropical areas that the commercial motive formed the predominant element in the imperial rivalries of the nation-states.  And even to-day it is over these areas that their conflicts are most acute.

A third motive for imperial expansion, which must not be overlooked, is the zeal for propaganda:  the eagerness of virile peoples to propagate the religious and political ideas which they have adopted.  But this is only another way of saying that nations are impelled upon the imperial career by the desire to extend the influence of their conception of civilisation, their Kultur.  In one form or another this motive has always been present.  At first it took the form of religious zeal.  The spirit of the Crusaders was inherited by the Portuguese and the Spaniards, whose whole history had been one long crusade against the Moors.  When the Portuguese started upon the exploration of the African coast, they could scarcely have sustained to the end that long and arduous task if they had been allured by no other prospect than the distant hope of finding a new route to the East.  They were buoyed up also by the desire to strike a blow for Christianity.  They expected to find the mythical Christian empire of Prester John, and to join hands with him in overthrowing the infidel.  When Columbus persuaded Queen Isabella of Castile to supply the means for his madcap adventure, it was by a double inducement that he won her assent:  she was to gain access to the wealth of the Indies, but she was also to be the means of converting the heathen to a knowledge of Christianity; and this double motive continually recurs in the early history of the Spanish Empire.  France could scarcely, perhaps, have persisted in maintaining her far from profitable settlements on the barren shores of the St. Lawrence if the missionary motive had not existed alongside of the motives of national pride and the desire for profits:  her great work of exploration in the region of the Great Lakes and the Mississippi Valley was due quite as much to the zeal of the heroic missionaries of the Jesuit and other orders as to the enterprise of trappers and traders.  In English colonisation, indeed, the missionary motive was never, until the nineteenth century, so strongly marked.  But its place was taken by a parallel political motive.  The belief that they were diffusing the free institutions