ECONOMIC EFFECT OF SANITARY WORKS. 133 
(ec) Preservation of street surfaces by water- 
ing 1% on 100,000 for 15 years i 15,000 
(d) Saving to municipal authorities in scaven- 
ging, 24% on all expenditure (Burwood 
experience) £400,000 . ee ih 10,000 
(e) Increase of population by progeny of 16, 930 
vigorous lives allowing 27°6 births per 
1,000 (Coghlan) 7,005 lives valued at 
£16 5s. ... Wy 113,831 
(f) and (g) possibly do not apply to Sydney. ten 
£12,526,151 
That eminent sanitarian Capt. Douglas Galton, R.E., in 
his presidental address to the Sanitary Institute of Great 
Britain, makes an estimate of the economy resulting from 
sanitary works as follows :— 
He compares the mortuary rates at Westminster with 
those in the Westminster Improved Dwellings which shows 
the mean age at death for males of the wage earning class 
who died after the age of 20 as being 47°6 years for the 
former, and 59 for the latter, the result being about 11 
years additional duration of life owing to improved sanitary 
surroundings, and consequently a profit to the community 
by reason of increased earning power. By referring to 
Neisson’s tables, he finds that 6 would be a fair average 
deduction for sick time between the ages of 47 and 59, and 
he therefore takes the increased earning power as that due 
to 11 years less 6% or 10°34 additional years of life. He 
allows £1 per week for the value of this earning power for 
each head of a family, and calculating for 10°4 years upon 
a 4% basis he finds the present value of the increased earn- 
ing power. Now if we apply this method to the case of 
Sydney, assuming five persons to each family for a popula- 
tion of 411,762, we have 82,352 families, the value of whose 
increased earning power for say 10 years would be in 15 
