FLOOD SILT OF THE HUNTER AND HAWKESBURY RIVERS. 191 



The FLOOD SILT of the HUNTER and HAWKES- 

 BURY RIVERS. 



By Professor T. W. Edgeworth David, b.a., f.g.s., f.r.s., 

 and Acting Professor F. B. Guthrie, f.i.c, f.c.s. 



[Read before the Royal Society of N. S. Wales, October 5, 1904.~] 



I. — Introduction. 

 II. — Bibliography. 

 III. — Area of Hunter and Hawkesbury Deltas and character of their 



deposits. 

 IV. — Volume of flood water. 

 V. — Amount, chemical composition and value of silt deposited by flood 

 waters. 

 VI. — Rate of accumulation of silt of Hunter Valley in relation to age of 

 Hunter Delta. 



I. — Introduction. 

 The Hunter Delta area is in its upper part one of the 

 most fertile districts of New South Wales, especially the 

 portion which extends from a little below Raymond Terrace 

 to a short distance above West Maitland. The fertility of 

 this region, one of the best lucerne producing areas in this 

 State, is due to the rich character of the flood silts, which 

 have proved to that district almost as great a boon as the 

 Nile mud to Lower Egypt. As much as \\ tons of lucerne 

 are produced per acre, and five crops are obtained a year, 

 their average value being about 35/- per ton. 



During the recent flood of July 12th, 1904, it occurred to 

 the authors that it would be interesting for scientific and 

 economic reasons to estimate the amount and chemical 

 composition of the silt in the water brought down by that 

 flood. We wrote to Mr. A. J. Prentice, b.a., of West 

 Maitland, asking him to secure samples of the flood water 

 and flood mud. He very kindly obtained both, and for- 



