THE WATER OF SOILS. 233 



the ferrous compounds, and the conversion of the pyrites first into 

 ferrous sulfate, and subsequently into innocuous, yellow, insoluble 

 ferric oxy-sulfate. 



Ferruginous Lands. The injurious effect of the swamping 

 of ferruginous lands has been especially conspicuous in some 

 of the irrigated rolling lands of the Sierra Foothills of Cali- 

 fornia, where orchards planted in relatively low ground and 

 in full bearing have succumbed to the poisonous effects of the 

 ferrous carbonate formed in the subsoil, long before the water 

 had risen so high that, had the trees been grown afterwards, 

 they would have adapted their root system to the existing con- 

 ditions and fared moderately well at least. Underdrainage of 

 the lower lands is, of course, the only possible remedy for this 

 state of things, although even then the root-penetration is much 

 more restricted, and therefore natural fertility of much 

 shorter duration, than would have been the case without the 

 rise of the irrigation water. 



It is thus clear that in the practice of irrigation, the liability 

 of injury to the lower ground by " swamping " through the 

 rise of the ground water should always be kept in view; that, 

 in fact, irrigation and provision for drainage should always go 

 hand in hand. The legal provisions facilitating the rights-of- 

 way for irrigation ditches should be made equally cogent with 

 respect to drainage. 



