ECONOMIC EFFECT OF SANITARY WORKS. T3u 
(a) Increased value of house property. 
(b) Deterioration of merchandise saved owing to clean 
well watered streets. 
(ec) Preservation of street surfaces by watering. 
It might be noted in reference to items b and ¢ that the 
City of London in 1880 spent £200,000 in watering the 
streets, and it was reckoned that £200,000 was saved to 
the shopkeepers by the outlay; asthe population of London 
is ten times the population of Sydney, the sum I have set 
down in my estimate further on, as the saving per annum, 
is just one-tenth of the saving in London. 
(d) Saving to municipal authorities in scavenging. 
(e) Increase of the population by the progeny of lives 
Saved. 
(f) Saving to commercial concerns by the use of pure 
water for boilers and engines. 
In connection with this item it may be mentioned that 
in large boilers used for commercial purposes the deposit 
of scale is a nuisance, and its removal a costly matter. 
It is well known that the presence of scale increases 
the consumption of fuel on account of its non-conducting 
properties, and it has been demonstrated by experiments 
that +sth of an inch of scale requires the expenditure of 
15; more fuel in the furnaces, and + inch of scale 607 more 
fuel. Further, the presence of scale necessitates the in- 
creasing of the heat in the boiler plates, which injuriously 
affects them by reducing their tenacity: experience shows 
that when scale has accumulated to a thickness of $ an inch, 
it requires 7007? of heat in the boiler to raise the steam toa 
temperature of 320° Fahr. with a working pressure of 90 Ibs. 
which introduces a tensile stress in the plates far in excess 
of the mean maximum tenacity of 65,000 tbs. per square 
inch of sectional area. Thus hard water or water contain- 
ing solids is bad for feeding boilers, and means increased 
