XLVI. H. D. WALSH. 
10. A sample of zinc sheathing taken from the bottom of a 
pontoon at Circular Quay, after 12 year’s service. 
11. A portion of timber showing the size of the holes bored by 
Cobra at the head of the Myall River. 
12. A portion of an oregon beam taken from Sydney Harbour, 
showing the destructive work of the Limnoria. 
13. Cobra taken from piles in Sydney Harbour. 
14. Sphaeroma taken from piles at Miller’s Point. 
THE AVAILABLE WATER DERIVABLE FROM GATHER- 
ING GROUNDS, THE LOSS, THE REASON FoR SUCH 
LOSS, AND THE RELATION BETWEEN RAINFALL 
AND DISCHARGE oF THE MURRAY RIVER AND ITS 
TRIBUTARIES. 
By R. T. McKAY, Assoc. M. Inst. C.B. 
[With Plates XXI.- XXII] 
[Read before the Engineering Section of the Royal Society of N. 8S. Wales, 
September 19, 1906. ] 
THE author has studied the problem of ‘‘ Relation of Rain- 
fall to Run-off ’’ of the Australian rivers for many years. 
It became his duty as Secretary and Professional Assistant 
to the Interstate Royal Commission on the Murray River, 
appointed to inquire into the just allotment of the Murray 
River and its tributaries for the purposes of water conser- 
vation, navigation and irrigation, to investigate the 
questions forming the subject matter of this paper, so 
that the observations are based upon a personal knowledge 
of the country, a close study of the geological formation, 
climatic conditions, etc. 
It is proposed to deal with the Murray River and its 
tributaries, which the author has traversed from mouth to 
