PART 4<.] Center: Note on Reh or Alkali Soils and Saline Well waters. 
263 
Accumulation iu baBins. 
iire undergoing rapid decay the production may be profuse. Also all water, 
I'iver, canal, or underground, that has washed over or filtered through the 
ground, contains similar salts and promotes their further production. 
20. The simplest case of accumulation is that of a closed basin like the Utah 
Basin. The surface water washing the salts off the 
ground has no escape to the sea, and fonns an inland salt 
lake. The soil in such cases is very saline, except in places where there is slope 
to allow thorough surface washing by rainfall, or permeability to allow the sur¬ 
face salt to bo washed down to a deep ground water. In the centre of the 
dej)ression both the surface and sub-soil and the sub-soil water are loaded with 
salt. The efflorescences in Utah closely resemble those in the Punjab, the main 
common ingredients being sulphate of soda, common salt, and often sulphate of 
magnesia. In some places there is a large amount of carbonate of soda, iu 
others borax is present. In the Caspian Basin the main ingredients are sulphate 
of soda and common salt. The very opposite case is a hilly or undulating country 
with sufficient rainfall and good natural surface drainage, the strata of which are 
also inclined, thus allowing of natural sub-soil drainage till the underground 
water finds an outlet at the outcroiss of the strata, or where they are laid open by 
natural sections of the country. Here the salts continually formed are either 
washed off the surface or are carried down to the sub-soil water which drains 
them off. 
21. In examining the state of things in the Indo-Gangetic plain, it is neces¬ 
sary to consider the structure of the countiy. The 
Himalayan axes stretching along the north of the plain 
are elevated cores of granitic gneiss flanked by mctamoi'phic and limestone rocks. 
To the south of this is the Siwalik fringe with its duns, consisting of clays, sand¬ 
stones, and conglomerates. These are fresh-water deposits formed by river and 
torrent action in the tertiary period, and having suffered displacement by the Hima¬ 
layan elevation, they are seen to pass with great undulations and numerous frac¬ 
tures under the strata of the plain. This formation conducts water under the 
jilain. There succeeds to this the recent gravel deposits from the outer hills, 
brought down by river and torrent action, similar to that which caused the 
Upper Siwaliks, and known as the Bhabar. This is extremely porous, and a 
great part of the water of the streams j)aBsing over it sinks into the ground and 
issues in springs at a lower level in the adjoining part of the plain, which is 
known as the Terai. Part also .sinks beneath the plain and raises the ground- 
water level. The great alluvial idain itself is composed of horizontal strata. 
Near the hills are gravel deposits, but further off the soil and sub-soil to 
an unknown depth are composed of deposits of clay, sand, and mixtures 
of the two in various projjortions, according to the stream or lake action that 
deposited them. Diffused through these are found mica and small cpxantities 
of carbonate of lime, which makes soils more or less marly, and iron oxide 
which gives them a yellow or red colour, and minuter amounts of sulphate 
of lime and other salts. Prom numerous well sections it is seen that these alter¬ 
nating permeable and impermeable beds of sand and clay are not continuous, but 
that they thin out and are replaced horizontally by others. This is observed even at 
Accumulation iu plains. 
