J. W. BOULTBEE. CLXXIII. 
to be the nature of the soil in regard to ‘perviousness’ and 
‘lightness’ on the one hand, and ‘closeness’ and heaviness’ on the 
other. For light soils hold a smaller amount of water in their 
pores than heavy ones, and permit more readily of ‘leaching’ 
through, by which the soil may be freed of its alkali salts. Clay 
soils, on the contrary, hold a large amount of water more tenaci- 
ously, and it is dificult, sometimes impossible to effect ‘leaching 
out’ of alkali salts unless by the aid of the underdrains. 
‘These preliminaries being understood, it is not difficult to see 
why and how alkaline irrigation water may be used with impunity 
on some lands while promptly fatal to the producing powers of 
others: one and the same amount of irrigation water may in sandy 
land readily penetrate to the natural subdrainage, thus preventing 
the accumulation of alkali in the soil by surface evaporation ; 
while used on an “Adobe ” it will not only penetrate to the sub- 
drainage, but, remaining within a few feet of the surface, will in 
a short time evaporate there, carrying upward with it the entire 
mass of alkali salts in the soil undiminished. Jn such lands, it is 
only by long soakage that the alkali salts can be sensibly diminished; . 
it is utterly idle to attempt to wash them off the surface by a rush 
of water, for at the very first touch the very strong solution first 
formed is absorbed into the dry soil and thereafter penetrates 
downwards instead of upwards. It is thus obvious that when we 
can apply to a fairly pervious soil an amount of saline irrigation 
water large enough to wash out into the subdrainage any former 
accumulation, and when this operation is repeated at intervals 
not too long, or surface evaporation allowed to progress to too 
great an extent, relatively strong saline waters may be used for 
ordinary culture plants with impunity, they being there substan- 
tially under the same conditions as the luxuriant vegetation com- 
monly found on the margin of alkali lakes. But itis quite other- 
wise when the same water is used according to the ordinary 
practice of irrigation, viz., only to the extent required to wet the 
root system, repeating this wetting at such intervals as may be 
required for the welfare of the crop, but never to such an extent 
