PROGRESS AND PUSITION OF IRRIGATION IN N.S.W. 399 
ledge of the facts. The subject is one which received much 
attention, both from the irrigation engineers and from the land 
settlement officers. For many years it has been well known in 
India that irrigation should not be allowed in places where the 
soil is much impregnated with salts or where the’ subsoil drainage 
is defective. So long ago as 1862, General Strachey of the Royal 
Engineers, lucidly stated the case as follows :—“ The salts known 
as “reh” are contained in the soil. If canal percolation takes 
place, it may at length proceed to such an extent as to saturate 
the subsoil with water. The surface being at the same time 
exposed to sun and air, becomes heated, and continual evaporation 
goeson. The. water lost by the surface evaporation is replaced 
by moisture drawn up from below by capillary action. The water 
coming from below contains a certain quantity of the soluble salts 
of the soil which it has taken up on its way: as the water evapor- 
ates at the surface the salts must be left behind, and a constant 
accumulation of the salt takes place on the evaporating surface. 
Where such efflorescence takes place at a distance from a canal, 
and where no free percolation takes place, it may possibly be 
explained by the action of an impervious stratum of clay (or kun- 
kur) at some depth below the surface, which arrests the descent 
of water derived from the fall of rain (or irrigation), and accumul- 
ated from a large area into some natural depression, and held, as 
it were, in a basin, though of course diffused in the subsoil from 
which the great summer heats at length extract the whole of it 
with the same result as before suggested.” 
This theory may not meet all cases, but it is recognised that it 
has very wide application. Hence, when it fell to my lot to take 
charge of the first irrigation which was started on the Lower 
Ganges Canal, I had special instructions in accordance with the 
principles here laid down. In the early days of the large irriga- 
tion works in India, and before this question was understood, 
there is little doubt that in some instances the saline efflorescence 
was spread by injudicious irrigation ; but precautionary measures 
were subsequently instituted, and more recently the Indian 
