DESERT SCENES IN ZACATECAS 439 



chilis are the principal garden crops, and flowers (poppies, asters, roses, 

 etc.) in pots or beds in the patios or dooryards of nearly all dwellings, 

 however humble. Fields of corn and barley, with calabasas (squashes), 

 are scattered about the plain not far away, where crops are matured in 

 the short season of the summer rains. Their corn planted in July is 

 harvested in October, its growth hastened by irrigation of a primitive 

 sort; running a ditch along the face of the slope, the ranchero collects 

 the run-off from the rains and directs it on to his field. On some of 

 these fields corn grows to the height of ten feet with a degree of luxuri- 

 ance that would gladden the heart of a northern farmer. 



Although no permanent streams of any consequence exist, yet the 

 rapid drainage of the land makes feasible a mode of existence other- 

 wise impossible. The herdsman pushes out away from walls and springs 

 and establishes himself in the midst of the desert. Choosing a place 

 where the land lies to form a basin or wide valley, he throws a dam 

 across the mouth and collects the run-off from a large area. For this 

 purpose a gently sloping drainage basin is preferred, else the labor of 

 building the dam will come to naught in a few years by the reservoir's 

 becoming filled with silt and drift; moreover, the rushing torrent may 

 cut through the embankment and drain the tank dry. I have seen old 

 tanks which had been filled to a depth of fifteen feet or more, and as the 

 earthen dam was finally cut through, the later floods had sluiced down 

 an arroyo through the flat sedimentary plain above. So the tanks in 

 such situations are short lived, but where fed by the gentle drainage of 

 a gravelly plain they may last indefinitely and supply water the year 

 round to large herds. Frequently these tanks hold water covering sev- 

 eral acres at the height of the dry season, and when at its deepest it may 

 assume the proportions of a small lake. Some of the dams are strong 

 and well-built structures of stone masonry a half mile or more in 

 length and ten to twenty feet in height. To the " tanques " come the 

 horses, the mules, the burros, the sheep, the goats and every other 

 animal of the desert ; they drink the turbid liquid, they wade in it, they 

 bathe in it, they discharge into it, and all around the margin is a fringe 

 of greenish drift and scum, but it is water in a thirsty land and man is 

 grateful for it. It is the objective camping point in the day's travels 

 and at noonday the cool shade on its banks is the favorite resting-place 

 for man and beast. 



From one to two and a half feet of rain falls on this land in a year, 

 depending partly on the altitude and local conditions. Eecords of rain- 

 fall at Chihuahua and San Luis Potosi show 10.86 and 10.41 inches, 

 respectively, for one year (1901), and at the city of Zacatecas the aver- 

 age for ten years (1897-1907) was thirty-one and a half inches. The 

 precipitation at Cedros for one year (1907-8) was about eighteen 

 inches. 



