85 



In another lagoon, near by, of great depth of water (8 to 

 BO feet), no water- weeds grew and no birds congregated, the 

 impurity was :— 



Chlorine 2-0 grains per gallon. 



Free Ammonia -00 ] 



.,, • -n A • o< I Parts per million. 



Albuminoid Ammonia •24 I ^ 



This water gets its organic impurity from the leaves of over- 

 hanging trees. 



Now I have observed over and over again, not in Queens- 

 land alone, but in various other countries, that water-weeds, 

 rooting at the bottom, will not grow in fresh water rivers and 

 lakes provided there be no shallow parts, no parts less than six 

 ieet deep, and I have observed that where there are no water- 

 weeds there are no free alga-, neither will Duck-weed (Leunui) 

 and Azolla grow ; the waves soon cast on shore these floating 

 plants ; whether the same would apply to the Water Hyacinth is 

 doubtful. 



On Stradbrook Island there are several large fresh-water 

 lakes with deep water (20 feet) free from water- weeds, fash and 

 birds ; the water is practically pure ; by preventing the leaves 

 from over-hanging trees entering the lakes, the water would 

 remain as pure as rain water in an ordinary galvanised iron 

 tank. 



It is true that the large Water-lilies, particularly the yellow 

 one {Xui>har lutca H.K.), can grow in water up to ten feet, but 

 in order for them to do so, they must be well established in 

 shallow water and gradually creep into the deep water ; ten feet 

 seems to be about the limit at which they will grow. 



When growing in water ten feet deep the slightest increase 

 in depth by rain causes them to die. If well rooted specimens 

 Tae sunk into water over six feet deep they will die, at any rate, 

 that is my experience. 



It is manifest the-n that were a water reservoir constructed 

 so that no parts would be less than six feet deep, water-weeds 

 would not grow in it. 



The Enoggera reservoir could be made to contain twice the 

 quantity of water it now does and the water would be pure. 

 Sooner or later the water-supply for Brisbane will have to be 

 augmented ; I believe the cheapest and best way to do this would 

 be by deepening the Enoggera reservoir. I suggest that the 



