400 PROCEEDINGS OF SECTION E. 



between Mulwala and Echuca, I found distinct evidences of 

 percolation in a north-westerly direction — that is into New South 

 Wales. Judging from the physical conditions of the district, I 

 suggested that probably it would be found that in the part of the 

 Murray between Echuca andthe junction with the M urrumbidgee 

 there is a westward percolation — that is into Victoria — and the 

 river gaugings which have since been made tend to confirm this 

 opinion. 



When we consider the great extent of the districts which contri- 

 bute either nothing or very little to the supply of our western rivers 

 and the great distances which these rivers flow without receiving 

 any tributaries, but with diminishing influences constantly at 

 work, thei'e seems little left to answer in regard to the question, 

 " What becomes of our rainfall ?" If there be any who still 

 entertain doubts on this subject, these doubts will probably 

 remain till the Government Astronomerdetermines experimentally 

 in the western district the rate of evaporation from shallow clay 

 pans and from earth kept saturated by capillary attraction. 

 Meanwhile I may recall a fact in connection with this which came 

 under my notice when I was engaged in compiling technical 

 information for the Water Commission. If the two lakes, which 

 combined are known as the Narran Water, were tilled, tlie extent 

 of the surface is so great that an average flow of one hundred 

 and ninety cubic feet per second would be required throughout the 

 year merely to balance the loss by evaporation — that is assuming 

 the latter at six feet per annum. Possibly this rate may be too 

 high ; but even if it were reduced by half, evajDoration, and absorp- 

 tion by vegetation would account for the disappearance of the 

 entire supply carried into the lake. 



During periods of drought when the ground becomes parched, 

 the beds of clay pans as well as hard and clayey ground in general, 

 become cracked and fissured ; and when rain falls, considerable 

 quantities of water flow into the cracks so formed. There is, 

 however, every reason to believe that by far the greater portion 

 of the water which thus disappears is absorbed by the soil within 

 a few feetbf the surface, and that its eflect is merely to restore 

 to the soil its normal proportion of moisture. In confirmation of 

 this it is found that after the downward flow continues for some 

 time, the clay or other soil expands, and closes the cracks ; so 

 that the ground becomes to all appearance as impervious as before. 



The scanty rainfall, the high rate of evaporation, and the un- 

 certainty of the supplies of water in the rivers and creeks 

 throughout a very large proportion of tlie country west of the 

 Dividing Range, combine to give special value to underground 

 streams. It has already been suggested that, as a rule, under- 

 ground supplies depend on percolation at the higher parts of the 

 drainage areas, and the reasons for this are not far to seek. In 



