OUTBURST OF SPRINGS IN TIME OF DROUGHT, 205 
supply of the creeks and springs, which after having dried out or 
dwindled down in the late drought, suddenly and without apparent. 
cause began to flow again, we find that the generally accepted 
theory, though applicable to some of our permanent and unvari- 
able springs, does not apply. 
The creeks and springs, of which I have carefully examined a 
considerable number, are fairly permanent in their flow in ordinary 
seasons, though many of them were not so until after the natural 
growth of Eucalyptus timber on the upper part of their watersheds. 
had been ringbarked from twenty to thirty years ago. In all of 
them the source from which the water flowing in their channels. 
is derived is a quantity of porous and somewhat spongy soil, of no 
great depth, resting on impervious strata of rock or clay, with a 
slope more or less steep in the direction of the creek or spring. 
In some cases this spongy soil is only a few hundred yards in 
extent, and in others a few miles; nowhere, as far as I am aware,. 
is there any holding back of the water by an impervious bar or 
dam of rock or clay. In normal seasons the sponge is filled to the 
point of saturation by the inflow of the rainfall from the surround- 
ing hills, and as it is held back like the water in an ordinary 
Sponge by capillary attraction and friction, it escapes slowly at 
the lowest level into the channel of the creek, thus maintaining 
an even and regular flow from one rainfail until the next. When 
the country is- suffering from one of our general droughts, the 
characteristic of which is an atmosphere of extreme dryness and 
an almost total absence of rainfall for many months, evaporation 
of course proceeds very rapidly over the whole surface of the 
sponge which forms the source of supply of these little creeks and 
springs, until at the lower levels, which are generally quite shallow, 
the rate of evaporation is so great as to dry it up, down to the 
impervious underlying strata. Then the water disappears from 
the creeks and the springs dry up, but all the time the water 
stored in the upper and thicker parts of the sponge which have ~ 
not yet been dessicated, is still moving down slowly along the 
slopes towards the creeks or outlet of the springs. The rate of 
