BACTERIA AS EMPIRE BUILDERS 185 



only very slowly as the density of the population slowly 

 increased. As a result they underwent evolution, and are now 

 able to persist even in the towns and cities of the United 

 States, though, as their high mortality shows, with difficulty. 

 Judging from the fate of Negro colonies in Europe and Asia 

 there can be but little doubt that a new immigration of 

 Africans into America would now have a speedy and 

 disastrous termination. 



307. After the discovery of America the principal mari- 

 time races of Western Europe competed for its possession. 

 Spain and Portugal, then powerful nations, had the first 

 start in the race, and chose the seemingly richer tropics. 

 But the forests of the centre and South were defended by 

 malaria, which raised a barrier against immigration, and by 

 heat and light, which raised a barrier against tuberculosis. 

 Moreover, the Spaniards and the Portuguese intermarried 

 freely with the aborigines, and the mixed race which resulted 

 inherits in half measure the resisting power of both stocks. 

 At the present day this mixed race, with a leavening of 

 mulattoes and of pure Spaniards, Portuguese, and Negroes, 

 inhabits the cities and more civilized parts. Even in tropical 

 America the pure aborigines are found, speaking generally, 

 only beyond the verge of civilization. Farther South the 

 disappearance of the natives has been more complete, and the 

 cooler, healthier, and more open pampas are settled by a race 

 more purely European. 



308. The weaker British and French were shouldered into 

 the seemingly inhospitable North. But the British won the 

 battle of Quebec and the French immigration soon ceased. 

 That little fight is half forgotten, but it is doubtful if any 

 battle in all history had results half so important. It placed 

 all North America in the grasp of the Anglo-Saxon, and gave 

 his race enormous space for expansion. Unchecked by 

 malaria the new-comers gathered into communities and built 

 towns and cities such as those which across the Atlantic were 

 the homes of tuberculosis. The cold forced them to admit 

 little air and light into their dwellings. The aborigines 

 melted away from the borders of the settlements. Under the 

 conditions there was little intermarriage. In that climate 

 Indian women and even half-caste children could not exist 

 within stone walls. The few white men who took native 

 wives preserved them only while living a wild life remote 

 from their kin. 



309. The British conquest of North America and Austra- 

 lasia resembles the Saxon conquest of Great Britain. The 



