140 Failure of the Yan Yean Reservoir. 



account for their enormous waterslied, is the same which has 

 led all other scientific men to the very opposite conclusion. 



If, according to their view, cultivation of the soil diminishes 

 the rivers, England of all other countries ought to have the 

 fewest and the smallest in proportion to the rainfall, and the 

 extent of surface, whereas, it is exactly the reverse, and, in 

 these respects Australia is the very antithesis of England. 



A barren, uncultivated and impenetrable soil, absorbs no 

 moisture from the atmosphere, and is very unfavourable for 

 the deposition of dew. 



Luxuriant vegetation absorbs large quantities of moisture 

 during the day, and is most favourable for the deposition of 

 dew in the night, and the surface, being protected from the 

 direct rays of the sun, is always cool and moist, and the rain 

 readily percolates through the soil to supply springs and rivers. 



Mere surface Avater adds little to rivers, except in floods : it 

 is that which percolates through the soil, and traverses either 

 the superficial, or deep strata, that forms the principal and 

 permanent supply of rivers. 



A compact and impenetrable soil, such as the Committee 

 believe to be most favourable for river supply, is in reality 

 the worst adapted for that purpose, and it is only in the 

 immediate vicinity of rivers that mere surface water can 

 reach them. 



The capillary attraction of the soil is too great to allow the 

 rain water to travel over any extent of surface. The varying 

 inclination of the surface also, and numerous other obstacles, 

 oppose its motion. 



Their illustration of the great watershed of the Dandenong 

 ranges is worthy of notice. Because the surface soil is ankle 

 deep with water in wet weather, they conclude that the 

 watershed must be very abundant, whereas, the opposite 

 conclusion is the more legitimate deduction. The rain, which 

 is so firmly held in the surface soil as to convert it into 

 swampy or boggy ground, cannot reach the rivers at all. It 

 remains there only to be evaporated and lost. It is the geo- 

 logical formation of the ranges, and the close structure of the 

 granite rocks, which prevents the rain from draining through the 

 soil, and gives rise to swampy and marshy ground, even on the 

 sides and summits of the mountain, and the same condition 

 occurs in the slate formation, as for example in the swamps 

 above Tan Yean, where the water cannot readily percolate 

 through the fissures, or where there is a subsoil of heavy 

 stiff clay. 



