122 TYPICAL QUEENSLAND LAGOON 
I regret to say that I am unable to describe the results 
of experiments with this method on anything but a 
laboratory scale, but the results thus simply obtained are 
so very excellent as to warrant the assumption that if tried 
on a larger scale, an effluent would be obtained which would 
easily excel the best results obtained by any of the methods 
I have just described, at the same time requiring a very much 
smaller area of sand bed, on account of the much greater 
rapidity with which the water may be efficiently filtered 
after treatment in this manner. (Appendix XI.) 
One more system of water purification remains to be 
mentioned before I conclude, namely Dr. Moore’s method 
of destroying and preventing the growth of algae and bacteria 
in water supplies. 
The numerous experiments with this method and our 
lagoon water, which continued without cessation during 
a period of three months, thoroughly confirm the results 
obtained in America in similar lakes by Dr. Moore, or under 
his direction. 
The method used for the distribution of copper sulphate 
throughout the lake is to tow it in coarse bags behind boats, 
in this manner it is stated that 100 lbs. of the salt can be dis- 
tributed in 1 hour. 
The toxicity of copper sulphate is so great that on one 
occasion when experimenting with so small a proportion 
of the salt as 1 to 8 million of lagoon water, only a few protozoa 
remained in the water after treatment, whilst untreated water 
which had been standing under exactly similar conditions, 
contained at the end of the experiment as many as 1,320 
organisms per cubic centimeter. 
The satisfactory fact was also noted that the organisms 
which are most objectionable and most plentiful in this 
lagoon, showed the greatest sensitivity to the sulphate of 
copper. From the results of the experiments, I think it is 
safe to conclude that a strength of solution of 1 part of copper 
sulphate to from 8 to 10 million parts of water is sufficiently 
strong to effectively remove the obnoxious algae from this 
water, this proportion stated in other terms is equivalent 
to llb. of copper sulphate in every 800,000 to 1,000,000 
gallons of water. I consider also, that if this salt is added 
