556 THE AMERICAN JOURNAL OF SOCIOLOGY
decreases, and the cause is found in the continuous coldness of the summer. For the same reason the JEsquimos also decrease.
At St. Petersburg the deaths exceed the births. If the Slavs persist at the north of the continent, they owe it to their cross- ing with the Finns, and perhaps, more to the west, with the Samoyides.
Our conclusions may be summarized as follows in reference to the geographic distribution and natural limits of the human varieties and races, independently of other more special socio- logical conditions which might intervene and alter the natural causes properly speaking:
1. Excesses of climate do not agree with any race.
2. The blond races correspond to the cool and temperate regions. The south is generally forbidden to them.
3. The brown races have a greater power of acclimatization. At the north they are represented by the Lapps ; toward the equator they easily extend themselves, especially those that are the most accentuated.
4. It is necessary to distinguish between the small and great displacements, the temporary, the definite, and the periodic. The gradual and peaceful displacements are the most favorable.
Crossing favors acclimatization after a certain number of generations. The crossing may be made either with the indige- nous race or with other races similarly immigrated, but more acclimatable. It is advantageous in either case. A small amount of negro blood diminishes the tendency to contract yellow fever. At the Cape of Good Hope, in the United States, and always in Algeria new races are thus formed by mixture. In the wake of a high mortality a few survivors are enough to serve as a nucleus for a new and progressive population.
The climate, in reality, has not the absolute effects that the old political theorists, including Montesquieu, attribute to it. The frontiers which he raised up between populations are not impassable. We may suppose that the differences of varieties are themselves only the adaptations of the descendants of a single group primarily homogeneous, and that the geographical and climatic environments have gradually become differentiated
