50 



THE FAKMERS HANDBOOK. 



quoted in the same table shows how profound have been the changes 

 brought about by cultivation. In addition to the increase in plant food 

 shown in the table there are other changes affecting the mechanical nature 

 of the soils which are not there shown. The capillary power has been 

 reduced in the case of the sandstone soils and increased in the case of the 

 shale soils to about the same figure in each case. In the same way the 

 water-holding power of the sandstone soils has been increased, and that of 

 the shale soils reduced to the figures given in the table. 



The original sandstone soils contain, generally speaking, a comparatively 

 small amount of clay, whilst the soils from the shale formation are more 

 clayey in nature. Under cultivation the clay percentage in the sandstone 

 soils has been increased and that of the shale soils reduced to about 72 per 

 cent, on the average. The soils are no longer the poor, rather hungry soils 

 characteristic of these formations, but approach more nearly the composi- 

 tion of a good basalt soil. 



FLOOD DEPOSITS. 



The silt deposited by floods has a considerable fertilising value, and the 

 extraordinary fertility of many river flats which are subject to periodic 

 floodings is, undoubtedly, largely due to this cause. 



An attempt was made to determine the nature and extent of this deposit 

 in the case of floods in the Hunter and Hawkesbury Rivers in 1904.* 



In the following tables are given the composition of these flood waters 

 and the amounts of suspended matter (silt), and the chemical composition 

 of the silts : — 



Analyses of Flood Waters. 

 Analysis of Hunter Hirer Water. 



Total residue .. " .. 

 Volatile on ignition 

 Fixed residue 

 Matter in suspension . . . 



Analysis of Ha\ 



Total residue 

 Volatile on ignition 

 Fixed residue 

 Matter in suspension 



Both waters are slightly acid in reaction 



Analysis of Silt from Hunter River Water, 



* David and Guthrie— Journ. Roy. Soc. N. S. Wales, Vol. XXXVIII., p. 191. 



