198 T. W. E. DAVID AND F. B. GUTHRIE. 



Mr. Cuthbert Potts, Science Master at the College, who 

 kindly collected the samples, July 14th, 1904: — 



"The flood had receded from 42 feet to about 22 feet 

 above summer level when the sample was taken, but the 

 current was running fairly strongly. The water was taken 

 from the middle of the river, near the Kurrajong Bridge. 

 The silt may be slightly contaminated by the washings 

 from some recent diggings, but as far as possible I obtained 

 a true sample. The flood was not high enough to largely 

 break over the river banks, above Richmond, and so the 

 Richmond bottoms were only covered with a back water 

 washing back from about three miles down the river. This 

 back water carries much less silt than the river, and is not 

 considered to do the land so much good. The bottoms 

 round Windsor and further down the river were swept by 

 the current and obtained a fair deposit of silt." 



Mr. John Tebbutt, the Observatory, Windsor, has kindly 

 informed us that the flood began to rise on the 9th July, 

 and attained its maximum height of 40*1 feet above the 

 mean tidal level of the South Creek early in the morning 

 of the 12th July. 



Analysis of Hawkesbury River Water. 



Parts per 1000. Grains per gallon. 



Total residue = *145 or 10*15 



Volatile on ignition = '03 ,, 2*10 



Fixed residue = '115 ,, 8*05 



Matter in suspension^ '116 ,, 8*12 



Both waters are slightly acid in reaction. 



Analysis of Silts. 

 Analysis of Silt from Hunter River Water. 



Per cent. 



Insoluble in hydrochloric acid ... ... ... =79*25 



Soluble in hydrochloric acid — 



Oxide of iron and alumina (Fe 2 3 and A1 2 3 ) = 10*02 



Lime (CaO) = 1*55 



Potash (K a O) =* 0*09 



Phosphoric acid (P 2 Q 5 ) = 0*18 



