146 



PROCEEDINGS OF SECTION C. 



13._0N THE TRANSPORT OF MUD BY A RIVER IN FLOOD. 

 By THOS. STEEL, F.L.S. 



During an unusually heavy flood which occurred on the River 

 Yarra, Victoria, in the month of July, 1891, I took the opportunity 

 of making a daily examination of the amount of suspended mud 

 carried by the water. The samples were drawn from the river at 

 the Sugar Refinery, Yarraville, at a point just above the junction 

 of the Goode Canal with the river, and hence include the flood 

 waters of the Saltwater River and those of the Yarra itself, except 

 what escaped by the Goode Canal. In normal times at Yarraville 

 and for some distance further up the river is tidal, and its water 

 contains a large proportion of sea water. The suspended mud was 

 coagulated by the addition of a minute quantity of alum to a 

 measured volume of the water ; allowed to settle, the clear water 

 decanted and the mud collected on a tared filter, dried in the water 

 bath and weighed. The dry mud was then ignited and the loss in 

 weight noted. During part of the period of observation the chlorine 

 in the water was determined as an index of the amount of sea water 

 working up the river from Hobson's Bay. 



The table following shows the results of the observations. The 

 quantities are stated in parts per 100,000 water : — 



It is interesting to note how with the recurrence of rain a second 

 flood was in evidence on August 3rd and 4th, which brought down 

 on one day considerably more mud than on the heaviest day of the 

 primary flood. Doubtless this was due to the washing down of mud 

 which had been freshly deposited on the river banks and was dis- 

 turbed again by the rising waters. 



The Chief Engineer for Water Supply, Mr. Stuart Murray, 

 kindly furnished me at the time with the official departmental 

 estimate of the quantity of water flowing past the spot where the 

 samples were taken, during the period from 10th to 22nd July in- 



