30 



BOTANY. 



that of the Rio Grande receives its fertilizing in the frequent overflows to 

 which it is subject, and in the mud carried suspended in the water used for 

 irrigating. But unlike the Valley of the Nile, the overflow can hardly be 

 called periodic. Dr. Oscar Loew has furnished the means of a comparison 

 in his table, vol. iii, page 578 : 



Potassa 



Soda 



Lime 



Carbonate of lime 



Magnesia 



Oxide of iron 



Alumina 



Silicic acid 



Sulphate of lime 



Phosphoric acid 



Water and trace of organic matter 



Rio Grande Mud. 



I.784 

 0.795 

 1. 751 



5-19° 

 O.181 



14.890 



70.010 

 Trace 

 0.092 

 5.012 



99.705 



Nile Mud. 

 (Analysis of Homer.) 



0-473 

 0-533 

 1. 901 



3-717 

 O.762 



31.870 



54-585 

 O.245 

 Not determined. 

 5- 7oi 



99.818 



The comparison shows, as Dr. Loew indicates, more potassa for the Rio 

 Grande mud, but less phosphoric acid, than the mud of the Nile, whilst 

 the Nile mud has a greater absorptive power for moisture than the Rio 

 Grande, because of its greater quantity of hydrated oxide of iron. Except 

 the enriching material thus conveyed, such long tilled lands as those of the 

 older Indian pueblos have had no other fertilizer. And this fact confirms 

 Dr. Loew's statement that the water is the all-sufficient source of supply. 



In other localities, as the one he cites, three miles north of Silver Citv 

 (p. 579), he attributes the success in raising corn to a moist subsoil (water 

 being reached in 16 feet.) and deep planting of the seed. But in Southern 

 Colorado, in the San Luis Valley, where water is reached at a much less 

 depth, irrigation is still found requisite. 



The Valley of the Colorado Chiquito, though now hardly under the 

 domain of agriculture, might be expected to produce large crops of grain, 

 fruit, and vegetables when once water is furnished by irrigation* 



Indeed, at the foot of the Mogollon Mesa, and for some distance up the 



* I allude here to the npper portion of this valley. I have no personal knowledge of its lower part. 



