156 TANKS AND WELLS OF NEW SOUTH WALES, 
In the first place the mean rainfall must be considered, and by 
referring to the rain maps there appears to be a possibility that 
this has been over-estimated. These maps show that there are @ 
1: 7 1 f4 . ae Ll dase toaeiel 
eater 
of the watershed than there are on the levels occupying the central 
and more westerly sections ; and as the rainfall is greater on the 
eastern side, any preponderance of observing stations there must 
Sive an excess on the true mean, unless the area composed by each 
scarcely be considered a satisfactory factor 
th 
3 
statement that a flood in November, 1881, travelled from Bourke 
to Wilcannia in three days—this gives a velocity of seven miles ap 
but a very small percentage finds its way into the main channe’s; 
a term the —— all is greatest on the eastern side of pas oo 
2. ust expect to find that a larger proportional quantity | 
its way into the river, than when contrary conditions prevail 
epancy een the supposed mean ra 
discharge, as compared with the two other years quoted. - 
