SOILS OF THE ARID AND HUMID REGIONS. 419 



It might be thought that the desire to avoid the labor of 

 clearing the forest ground was the motive which guided the 

 choice of the ancient nations toward the cheerless-looking, tree- 

 less regions. 



But if we consider the cost and labor of establishing and 

 maintaining irrigation ditches, it certainly seems that a 

 stronger motive, based on the intrinsic nature of the case, must 

 have influenced their selection. Neither can we with any 

 degree of plausibility ascribe the preference for the arid open 

 country to the fear of enemies lurking in the forest, since war 

 was in early times practically the normal condition of man- 

 kind, and was waged with little hesitation wherever booty was 

 in sight. It has also been asked how the ancients could have 

 known of the high productive capacity of arid lands ; but no 

 one who has ever seen the springing-up of luxuriant vegeta- 

 tion after the periodic overflows of the arid-region streams, or 

 the same surrounding the springs in the deserts, would ask that 

 question. 



Irrigation necessitates Co-operation. Irrigation enterprises 

 can be accomplished in a very limited degree only by individ- 

 uals or even families. Its permanently successful execution re- 

 quires the co-operation of at least several social groups, ulti- 

 mately of communities and states, if it is not to give rise to 

 acrimonious contentions or actual warfare ; witness the " shot- 

 gun policy" resorted to in the arid West in times not very 

 remote. Irrigation, in other words, compels co-operative social 

 organization quite different from and far in advance of that neces- 

 sary in humid countries. And such organization is mani- 

 festly conducive to the preservation and development of the 

 arts of peace, which means civilization. The most ancient 

 systematic code of laws known to us is that of Hammurabi, the 

 king of arid Assyria. 



The high and permanent productiveness of arid soils induces 

 permanence of civil organization. In humid countries, as is 

 well known, cultivation can only in exceptional cases be con- 

 tinued profitably for many years without fertilization. But 

 fertilization requires a somewhat protracted development of 

 agriculture to be rationally and successfully applied in the 

 humid regions, and the Germanic tribes, like the North-Ameri- 



o 



can Indians, seem to have shifted their culture grounds fre- 



