2 
different. The sewage from any given number 
of houses can be estimated and provided for as 
a tolerably steady and continuous flow ; but the 
rain-fall in this country is not to be guaged thus. 
It would require at one time very large dis- 
charge pipes, and at another very small ones ; 
but pipes or sewers of large sections would be 
almost useless for the transmission of sewage, 
and indeed very mischievous, as retaining the 
solid portion of the matter they were intended 
to carry off. Surface water from streets, espe- 
cially if on a declivity and having a sandstone 
formation like most of ours, carries with it a 
quantity of silt, or fine sand. This, if conveyed 
into small pipes, gradually but surely chokes 
them — if into large sewers, forms deposits on 
their lower surface which become obstructions to 
the passage of sewage over them, arresting the 
solid portion and retaining it to accumulate 
noxious gases, which sooner or later escape and 
poison the atmosphere. And, moreover, if the 
sewerage pipes be laid down with regard to their 
efficiency as such, a sudden rush of storm water, 
being too great for their capacity, will burst 
them at the junctions. Hence surface drainage 
should be carried off by surface drains. The 
term “ surface drains” is not intended to mean 
the street-side channelling, as it is called, which 
is generally supposed to be, and is not, adequate 
to the purpose, but sunk channels of proper 
section laid to the required level. These 
channels need not be more than 9” in diameter, 
and about six inches in depth, laid close to the 
kerb. Their smooth surfaces offering no ob- 
struction to the water, it would flow with great 
velocity, and rarely exceed the channel they 
afford. The junctions should be curved so as to 
aid the flow of drains on the lower level, and 
the sizes should be graduated by the relative 
positions of the streets, increasing as they 
approach the point of final discharge. A very 
slight fall, such as 6 inches in 100 feet, is suffi- 
cient in such cases, but the channels should be 
laid truly and well bedded. The cost of repairs 
would in that case be inappreciable. 
For sewers, the first consideration is the main 
outfall, and this again has two points connected 
with it : — 1st. Whether the sewage is to be col- 
lected in a reservoir and employed as manure. 
2nd. If it is to be discharged into some conti- 
guous stream. 
Of late years there has . been much controversy 
touching the employment of sewage as a manure. 
Of its fertilizing power there is no question, but 
the economy of its conversion remains to be 
proved. Various processes have been invented 
for the deodorization, as it is called, of the 
sewage, and for the evaporation of the fluid so 
as to leave the residuum in the shape of a 
powder ; but the cost of the process seems in 
all cases to have exceeded the revenue it yielded. 
n If the local circumstances of a town render the 
collection of the sewage a necessity, then the 
best method of use for manuring purposes seems 
to be that of keeping the mass in a fluid condi- 
tion in an air-tight reservoir, and its conveyance 
in tank carts with pierced discharge pipes, like 
those of ordinary water-carts, to the place where 
it is to be used. This is not difficult, for the pro- 
portion of solid to fluid in sewage is exceedingly 
small. When the only natural outfall from a 
town is a fresh- water stream of limited capacity 
and subject in drought to shallowness, some 
such method as that described must be adopted 
or the stream itself will become a huge open 
sewer, poisoning the atmosphere and polluting 
the water for many miles. One or two philoso- 
phers have indeed asserted that the deodorizing 
power of fresh water is such as to neutralize the 
noxious gases held by sewage ; but, setting aside 
the question at what relative quantities the sup- 
posed effect ceases, it may be sufficient to say 
that the theory has as yet secured no adherent 
beyond its first propounders. 
When a broad and deep river, sufficiently 
affected by the tide to be salt, is available, there 
is no objection to a discharge of sewage into its 
waters, but the method is open to discussion. 
Some engineers advocate the construction of a 
mouth to the main sewer between high and 
low water mark, closed at flood and open at ebb 
tide. A self-regulating valve is easily appended 
to such an outlet. Others are in favour of the 
mouth being placed permanently below the low 
water level, the sewage being left to mingle with 
the stream as it best may ; and probably this is 
not merely the simplest but the least objection- 
able method, especially where, as in a tovyn like 
Brisbane, several outlets would be available and 
indeed necessary. Care, however, should be 
taken that the outlet is carried to as great a 
depth in the stream as the navigation will allow, 
and that its mouth is turned in the direction of 
the ordinary current. 
The outfall and its method being decided, the 
material form and size of the sewers is next to 
be considered. Any absorbent substance is ob- 
jectionable, as tending to the escape of noxious 
matter into the adjacent soil, and as hindering 
the flow of the sewage. Wood is obviously the 
worst possible material. Bricks, as commonly 
made, are also objectionable, for they are most 
generally of a very inferior kind, absorb almost 
as rapidly as ordinary soil, and the mortar joints 
soon give way. What are called dry brick bar- 
rel drains — i.e. formed of brick without mortar — 
are merely elongated cesspools. Glazed stone- 
ware is the best of all materials within the limits 
of size to what it can be applied, its smoothness 
offering no obstruction to the flow of the sew- 
age and its impermeability preventing the perco- 
lation of feculent matter into the soil. Next 
to this, hard-burned but slowly-burned bricks, 
made of strong clay with an adequate mixture 
of coal cinder (technically called breeze) set in 
cement, are most approved. 
Some years back, when the question of sewer- 
age received the attention it required, mucli dis- 
honest disputation took place as to the material, 
form, and size of sewers and drains — disputa- 
tion in which the advocates on both sides went 
to the most extraordinary extremes. Those who 
