86 Uakt, Eucaiypts about Cresivick and Clitncs. rvJ"^xxxVv 



it can penetrate at once below the roots of the smaller vegeta- 

 tion. The run-off of summer rain is very low, as is shown 

 clearly in the experience of the Ballarat Water Supply, of 

 which the catchment was, before recent additions, nearly all 

 volcanic country, and the water caught in a very dry year 

 onlj' a small proportion of the rainfall. Summer rain, in an 

 ordinary season, added very little to the water running in the 

 streams. 



It must be noticed also that the water which sinks in is not 

 all available to be raised again by capillarity to the soil. 

 Water easily travels through the cracks of the bluestone rock 

 below, except in so far as these cracks are closed by damp 

 clay from the weathering of the rock. Water which reaches 

 clean or dry cracks in the bluestone will descend to the natural 

 water-level ; in one old shaft at North Creswick this was found 

 to be 77 feet below the surface. No capillary action can 

 return the water by these cracks, as such action depends on 

 the passag'es being small. Water which reaches clean blue- 

 stone may be regarded as lost to the vegetation ; its only 

 possible effect is to keep the air moist in the cracks of the 

 rock, an effect which might perhaps reach the deeper soil- 

 cracks. ^Mining experience in the basalt plains amply 

 establishes this easy passage of water through the cracks of 

 clean bluestone, while at the same time surface holes in clay 

 and w'ater-courses continue to hold water in spite of pumping 

 out the water from the rock belovw The absence of a useful 

 supply of water below the soil is not due to impenetrability of 

 the soO and rock below, but to a kind of penetrability which 

 prevents the storage of water at a level from which it can 

 return, except in the clay, which is not deep, and can withhold 

 water from the plant to an important extent. 



The soil character makes the wetness of wet periods more 

 pronounced than in freer soils, and the dryness of dry periods 

 also more effective ; it intensifies the seasonal effects in which 

 summer drought is already serious. 



Reviewing the seasonal conditions in the plains, once the 

 plain is dry and cracked in summer very little advantage is 

 recei\'ed from the summer rain, and on this the grass has first 

 claim after any deficiency in what the clay itself can withhold 

 from vegetation is supplied ; shrubs might be worse off than 

 a tree, which could thrust its roots deeper. The cracks close 

 as the moisture increases in autumn, but an autumn growing 

 season is precarious. It may be late in the year before there 

 is ample water, with days already shortened and temperatures 

 falling. (A favourable autumn may i)roduce a considerable 

 response in the vegetation, as was seen in some districts in the 

 profusion of the flowers of Wahlenbergia in the autumn of 



