BDSSELL] AGEICULTUKE 87 



inches in depth. The Pimas tlo not practise rotation of crops, the 

 soil being so rich from silt which is ])erio(lically deposited by the 

 river at flood stage that the idea of exhausting it has never occurreil 

 to them. 



Irrigation was practised for unknowTi centuries by the Ilohokam, 

 and the course of their great canals can yet be traced for miles," not 

 only along the river bottoms, but also across the mesas where the 

 large water-worn pebbles bound together with caliche'' or deposited 

 lime must have recpiired iniinite labor for their construction. At 

 the first appearance of the Pimas it may be presumed that they used 

 the canals already constructeil by their predecessors, hence they 

 would be dull indeed if they could not maintain irrigation systems 

 suilicient for their needs. The testimony of the early writers is to 

 the effect that they ])ossessed canals larger than they required and 

 that the water flowed away from the fields in volume scarcely dimin- 

 ished from that at the head gates. The Gila has a uniform fall of 

 8 feet to the mile at this place, while the canals need not have more 

 than 2. 



As the water of the Gila and Salt rivers is strongly impregnated 

 with alkali it tends under certain conditions to deposit salts in such 

 quantities that the land is rendered unfit for use. The alkali rises to 

 the surface in an efflorescence that resembles snow in appearance. 

 From early descriptions of the country we learn that alkaline de])osits 

 were known while the tribe was yet under j)urely aboriginal con- 

 ditions." 



The Pimas knew, however, how to deal with this dilliculty — they 

 flooded the tract repeatedly and in this way washed the alkali out 

 of it. They declare that they never abandoned a piece of ground 

 because of it. 



No very reliable estimate of the total amount of land cultivated 

 by this people has been made.'' Each family cultivates from 1 to 

 5 acres. With an abundance of water and the new needs of the 

 tribe it is probable that the size of the individual holdings will rap- 

 idly increase. The farms are rectangular, arranged with reference 



a "The mode of canal construction employed by these puelilo builders [Ilohokam] was another indi- 

 cation of their patience and industrj'. Their canals are models for the modem fanner to imitate: yet 

 they could have been dug in no conceivable manner save by the laborious process of hand excavation 

 with stone or wooden implementa^ the earth l^ing home away by means of blankets, baskets, or rude 

 litters. Notwithstanding this, the outUnes of at least a hundred and fifty miles of ancient main irri- 

 gating ditches may be readily traced, some of which meander southward from the .Salt riv<'r a distance 

 of fourteen miles." F. W. Hodge, "Prehistoric irrigation in -Vrizona," -Vmerican Anthropologist, vi, 

 324. 



6 For an account of this formation see P. Blake, "The caliche of southern .\rizona: an example of 

 deposition by vadose circulation." in The Genesis of Ore Deposits, 710. 



c" We continued [fromCusa Grande] toward the west, over sterile plains. On all the grounds about 

 these buildings there is not a single pasture; but appear as if they had been strewn with salt." Mange's 

 Diary, in Schoolcraft, in, 303. 



d Garc6s. writing in 1775. stated that "Todos estos pueblos hacengrandes siembras de trigo, algunas 

 de maiz, algodon, calabazas y otras semillas, para cuyo riego tienen fonnadas buenas acequias, cercades 

 las milpas con cerco comun, y divididas las dc distintos duenos, con cercos particulares." I)oc. His. 

 Mex., 2d ser., i, 235. 



