STEPPES, DESERTS, AND ALKALI LANDS. 603 



ilization of the Aztecs and Toltecs was developed not in the won- 

 derfully prolific tierra caliente, but on the arid plateaus of Old 

 and New Mexico ; persisting while the builders of Palenque and 

 Copan had already passed into oblivion. It seems as though a 

 strange infatuation had possessed these ancient nations in the 

 preference given to bare, sun-scorched plains and mountains, as 

 against the cool shades of the forest-clad countries, which in later 

 times have almost monopolized the abodes of advanced civili- 

 zation. 



It may be said, of course, that forests offer the inconvenience 

 of affording concealment to a lurking enemy; a serious considera- 

 tion during the ages when a state of war was the normal condi- 

 tion of mankind. Again, it is said that the necessity of clearing 

 away the forest before cultivation was possible offered an obvious 

 inducement toward the utilization, first, of the treeless regions. 



The former consideration doubtless weighed strongly in the 

 first beginnings of settlement. And yet our Saxon forefathers, 

 both in the old and new continents, have managed remarkably 

 well in their forested countries, in the face of lurking enemies 

 both animal and human. As regards the difficulty of clearing the 

 forest lands for cultivation, it is amply offset by the necessity, 

 almost universally existing in treeless countries, of providing 

 irrigation if cultivation is to be anything more than a lottery. 

 For forests are limited by a certain minimum of rainfall, below 

 which regularity of crops is dependent upon artificial irrigation. 



In other words, the countries which have harbored most of the 

 ancient civilizations are regions of deficient rainfall and compul- 

 sory irrigation. And as irrigation means heavy investments of 

 capital or labor, hence the co-operation of many and the construc- 

 tion of permanent works : it necessarily implies the correlative 

 existence of a stable social organization, with protection for prop- 

 erty rights, and (in view of the complexity of the problem of 

 proper and equitable distribution of water) a rather advanced 

 appreciation of the need and advantages of co-operative organi- 

 zation. 



If, then, the general practice of irrigation is conditioned upon a 

 not inconsiderable degree of advancement in social organization, 

 shall we attribute the development of the ancient civilizations 

 referred to only to its conservative influence, or are there other 

 factors that have contributed toward the preference and long- 

 continued permanence of these polities or populations ? 



The high cost of irrigation is usually found to be compensated 

 by the high and regular production of the lands irrigated ; it is 

 almost a maxim that irrigated lands can support a much denser 

 population than those of countries in which rainfall is relied 

 upon for the production of crops, and where therefore frequent 



