BY A. MAULT, 191 
this matter would be of importance; but as it is into a large basin of 
salt water, it is of none, for it is in solution, and cannot pollute the 
shores of Sandy Bay, nor any other shore. But all other matters are 
in excess at the Rivulet—the total quantity of solid matter discharged 
there being two and a-half times as much as that proposed to be dis- 
charged at the Point. And it must always be borne in mind that the 
larger quantity is discharged into comparatively stagnant land-locked 
water, while the much smaller quantity is proposed to be discharged 
into running water, that is, the larger quantity is discharged where its 
polluting effect is certain to be the most marked and constant, and the 
smaller quantity where its polluting effect is equally certain to be the 
least, asthe purifying effect of the recipient water wiil be the greatest, 
The purifying effect of water is due to the action of the oxygen it con- 
tains. Mr. William Odling, the celebrated chemi-t, in his evidence 
given last November before the Royal Commission on the water supply 
of London, said—‘‘ Four tons weight of oxygen is contained in every 
hundred million gallons of water (1 ton in 112,000 tons) ; oxygen had 
power to destroy 4-5ths of its weight of organic matter. This oxydisa- 
tion is not a mere theory, but is based on solid fact.” Of course, in 
order that this oxydisation may be effected it is necessary that the 
organic matter should be exposed to the action of the oxygen in the 
water- should, in fact, be brought into contact with it. This can only 
be secured by continual movement of the water, hence the well-known 
purifying effects of running streams. 
Bearing all this in mind, it will be useful to note what is the effect 
of the daily discharge of the 26,000lb. of solid matter from the Hobart 
Rivulet into Sullivan’s Cove. This effect can be noted in the analysis 
above given only in the constituents that are absent from sea-water, 
that is, the nitrogen in solution and the matters in suspension, as the 
immense quantity of salt and other solids in solution in sea water alto- 
gether mask the effect of the comparatively feeble acditional quantity 
brought in by the Rivulet. It will be seen that to all practical intent 
the water of che Cove is as little polluted at 100yds. from the mouth of 
the Rivulet as it is in mid-stream, where the Rivulet cannot affect it, 
It is true that there are 4-100th parts of a grain more nitrogen to the 
gallon of water, but there 20-100th parts of a grain less organic matter 
in suspension. At 450yds. from the mouth of the Rivulet all trace of 
the effect of its discharge may be said to be lost, as the slight difference 
in the quantities of their constituents, when the water of the Cove 
there and that of mid-stream are compared, is attributable rather to the 
Kelly steps and Timber Wharf sewers than to the Hobart Rivulet. 
The question to be answered is thus shown to be :—‘‘If the discharge 
of 26,000lb. a day of solid matter into the comparatively still water of 
Sullivan’s Cove has virtually no appreciable effect upon it, what will be 
the effect upon it of the discharge of 10,400lb. a day into the tideway, 
600 yards further away ?” And we are asked to answer it, though we 
have proved the contrary, ‘‘that the effect will be disastrous.” Can the 
force of unreason go further? Perhaps it can; and in the nature of the 
proofs that are given of what will be the consequence of discharging 
sewage at Macquarie Point. To say nothing of Sydney sewage being 
traced across 1,000 miles of Pacific rollers to the coast of New Zealand, 
it is said that the fact that the Hobart Rivulet, when in flood on the 
18th of January this year, discoloured the waters of the Cove, showed 
what the effect would be of the proposed discharge of sewage at 
Macquarie Point. Now I gauged the water of the rivulet on that day, 
aad found that very nearly 1,600,900 tons of water were flowing under 
Campbell-street bridge in the day—about 160 times the dry weather 
flow, and 400 times the estimated discharge from Macquarie Point. 
At the lowest estimate I could make without analysis, this water con- 
tained three times its usual quantity of earthy matter ; that is, about 
