76 On the JBotany Watershed. 



clay, varying from two to three feet in thickness. The average 

 depth of the sand hills on both sides of the swamps above the 

 sandstone formation is about 30 or 40 feet. Thus we have a 

 gathering ground whose surface comprises about one-sixth bog, 

 and the remaining five-sixths pure sand, which is protected 

 from the wind and rays of the sun by a covering of low scrub 

 and brush-wood — and whose bottom is sandstone rock covered 

 with a stratum of clay — which will admit of no percolation 

 through it. This is, I believe, at once the most r.bsorbent 

 and the most retentive catchment that is known to exist 

 in any habitable part of the globe. 



Amongst all the sources of supply mentioned by the Water Com- 

 mission there is none which can be compared in value with this. 

 No similar locality has been found with an equal power of conserv- 

 ing water. It must be admitted that sand has greater absorbing 

 powers than any other soil, and the immense body of 

 sand I have described, extending as it does over so large an area, 

 absorbs the rain as it falls, and thus becomes saturated with 

 water. The absorption is so immediate and so perfect that no 

 puddle or run of water can be discovered on the surface of the 

 sandhills during the heaA^iest rains. The whole of the water 

 which falls on the surface being embodied in the sandhills, passes 

 down slowly by filtration, and after storm time the water may 

 be seen oozing out of the base of the hills into the swamps ; 

 by this means some is given off to the watercourse or rivulet 

 which passes through the swamps, whilst the remainder descends 

 farther down and is given ofi" to the stream or dams at lower 

 levels. The fact of this large basin of sand having a sandstone 

 bottom renders it quite impracticable for the water which has 

 been absorbed by the sandhills to escape in any direction but 

 towards Botany. Sooner or later the sand will give ofi" the 

 water by percolation, which it has absorbed during the wet 

 seasons, either to the adjacent stream, or at lower levels before 

 it reaches Botany. The watershed is so admirably formed by 

 nature that it loses nothing by absorption and very little indeed 

 by evaporation. Let it be borne in mind that the stream of 

 water which passes by gravitation through the tunnel into 

 Sydney has never yet, in the driest season, ceased to flow, nor 

 lias the stream which used to discharge itself into the sea at 

 Botany ; also that enormous quantities of water have run to 

 waste from this watershed into the sea at Botany during the 

 rainy seasons of the last twelve years that the pumping engines 

 have been at work, for want of storage room. When the tunnel 

 was gauged by order of the Grovernment in the year 1S52, the 

 quantity of water found passing through was 320,000 gallons 

 per diem. Since the year 1856 the number and lengths of the 



