20C T. W. E. DAVID AND F. B. GUTHRIE. 



The weight of this deposit in the case of the Hawkesbury 

 flood would be 27,561 fibs, per acre, or about yo the weight 

 of that left by the Hunter River flood. 



This would provide the land with a top dressing per acre 

 of the following fertilising constituents : — 



Lime 135 fbs. 



Potash 33 „ 



Phosphoric acid ... ... 22 ,, 



Nitrogen ... ... ... 29 ,, 



All the above estimations as to the amount of fertilising 

 material deposited are based on Mr. Prentice's assumption 

 that the deptli of the deposit in the case of the Hunter 

 River Hood averaged 2 inches. This appears a very high 

 average, but there are unfortunately no hydrographical 

 data available by means of which this can be checked. It 

 would be a matter of considerable national importance if 

 further data concerning the rate of flow, volume of water, 

 height of flood, and amount of silt deposited etc., could be 

 obtained during the period of such floods as those now dis- 

 cussed. This is a matter which might well engage the 

 attention of the engineers of the Public Works Department. 



VI. — Rate of Accumulation of Silt of Hunter Valley 

 in Relation to Age of Hunter Delta. 



As stated in the previous section of this paper, Mr. 

 Prentice estimates that approximately 2 inches of silt were 

 deposited over the upper part of the Hunter Delta by the 

 last flood of July 12th, but his observations were confined 

 to a comparatively small portion of the delta close to West 

 Maitland. Observations of this kind to be of real scientific 

 value, need to be taken over a large area ; this Mr. Pren- 

 tice attempted to do by inviting by advertisement the 

 furnishing of statistics by farmers and others resident in 

 the district, but he was unable to obtain any response. 



