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: 
Rio Grande Mud. | Ae om bes pres 
Potassa 1.784 0.473 
Soda ..-.-----2-- 22-202 2eeene cence eee eee 0.795 0.533 
Lime 1.751 1.901 
Carbonate of lime 5-190 3.717 
Magnesia ...... 0.181 0. 762 
Oxide of iron ..---- 
po on ee } 14.890 31.870 
Silicie acid 70.010 54-585 
Sulphate of lime Trace 0.245 
Phosphoric acid 0.092 Not determined. 
Water and trace of organic matter..........--. 5.012 : 5-701 
99.705 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 City 
(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 distznce up the 
*I allude here tothe upper portion of this valley. I have no personal knowledge of its lower part. 
