162 TANKS AND WELLS OF NEW SOUTH WALES, 
these shafts and be rapidly stored under favourable conditions as 
perature and evaporation, and at a depth from which it 
could be economically raised to the surface as required. 
2. Tanks. 
the surface by stock or otherwise ; that the soil in which the tan! 
1s to be excavated is of a retentive nature ; and in estimating this 
latter condition it must be borne in mind that many tanks which 
when first constructed lose water subsequently become thoroughly 
watertight, this result being due to the deposit of clayey 
water at the tank site which, after fi 
to the same level through an inlet pipe, can then be pumped over 
the embankment into the tank, ¥ 
en tanks are constructed in watercourses, the plan 
‘ 
im cases where the channel is shallow and the fall © ae 
the bed considerable, this dam is carried above the level of ihe ‘ 
creek ba and flanking embankments carried on the same Jere oe 
8 dam are continued up each side of the creek until they cut ®°— os 
