192 a W. M. HAMLET. 
of the gravest importance to city councils and local 
authorities. The gravity of the question is accentuated, 
because under present ordinary conditions the mains are 
being slowly but surely eaten away by the rusting process 
constantly going on, caused by the flowing water, so that 
their renewal, at no distant date must eventually be faced. 
The Sydney water supply as it comes from the catch- 
ment area consists of a soft water containing only three 
“ quarters of a pound of total solid dissolved matter in one 
thousand gallons (or eighty four parts in a million). But 
it is fully charged with air containing as it does 5°8 ina 
thousand of oxygen (5°8 cc. per litre). The carbonic acid 
taken up from the atmosphere amounts to about one part 
in a thousand. As soonasthis water comes into contact 
with bare unprotected iron in any of the mains, chemical 
action proceeds rapidly, and a very perceptible amount of 
ferric oxide is carried about in suspension until at the 
furthermost outlets and in the dead ends of the reticulation 
of pipes considerable quantities of red sediment make itself 
visible, giving the water a rather repulsive appearance. It 
is due to the particles of red rust in suspension together 
with some vegetable matter which has become precipitated 
along with it owing to nuclear action of the masses of 
ferric oxide. In some systems of water supply where a 
soft water is collected, notably at Aberdeen in Scotland, 
the pipes have been quite choked up with rust and had to 
be cleared by mechanical means. The storage and trans- 
mission of water can be successfully accomplished without 
deterioration or injury to the water, but only when the 
interior of the pipes and the joints of the mains are properly 
coated and protected by means of some material that is so 
insoluble in water as to shield the iron from attack. 
In the Sixth Report of the Rivers Commission the well 
known method of protection by means of Dr. Angus Smith’s 
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