92 
PURIFICATION or WATER 
IN DAM 
MR. MORRY, of the Queensland Department 
. of Agriculture, states that the water in a 
dam can be purified and the muddy matter 
in suspension be deposited by adopting the 
following method: Purchase 1 cwt. of 
ordinary commercial alum (not the purified, 
which is costly), also a similar quantity of 
sulphate of iron. Take two flat boxes ; bore 
a large number of small holes in the bottoms 
and sides; attach each box to two pine 
boards spaced apart for this purpose, allow- 
ing for the exposure of as much of the 
bottoms as possible. Use about 20 lbs. of 
each of the above chemicals and mix to- 
gether in the box. Weight the improvised 
raft so as to submerge the box to a depth 
_of three or four inches. Attach light ropes 
or wires to the respective rafts and draw 
them backwards and forwards in the dam. 
The action of the alum and sulphate of iron 
will soon bring about the desired change in 
the quality and colour of water. If the 
expanse of water is large more boxes will 
be required. Three or four of these box- 
receptacles can be allowed to float in 
different parts of the dam. 
