198 
NATURE 
[ ¥uly t, 1886 
public opinion will soon, if it does not already, regard | 
small-pox hospitals as possible centres of infection, and 
will insist on their removal outside inhabited areas. | 
The compulsory notification of infectious diseases to | 
sanitary authorities, either by the householder in whose 
house the case occurs, or by the medical attendant, or by 
both, has been adopted in numerous provincial towns 
during the last five years. This measure has done much 
to furnish the authorities with early information of the 
occurrence of infectious disease which would not other- 
wise have been obtained, and such information has 
doubtless enabled the sanitary officials to stamp out many 
an epidemic in the bud, which might otherwise have 
reached large dimensions. The more universal adoption 
of a measure of compulsory notification in our large towns 
is urgently needed. 
In the domain of domestic sanitation the advances of 
recent years have been mostly limited to the practical 
applications of sound principles already acquired to the 
carrying out of works of construction, drainage, or water- 
supply of the dwelling. Houses built for the use of the 
well-to-do classes (not those of the speculative builder) 
in recent years will most generally be found to be planned 
and fitted on modern sanitary principles. Thorough 
ventilation of the drain and soil-pipe, disconnection of the 
waste-pipes of baths, sinks, and lavatories, and of the over- 
flow-pipes of cisterns from the drainage system, are now 
understood to be necessaries of modern life. A break 
in the connection between the house-drain and the public | 
sewer by means of a manhole chamber and water-seal or 
trap, though not considered necessary or desirable by all, 
is now very usually practised. We cannot doubt that the 
air of a public sewer 1s sometimes the means of disseminat- 
ing disease, and any method which practically excludes 
such a source of danger from our houses is one to be 
encouraged. As knowledge extends, the simplest form of 
apparatus is found to be the best; many of the more | 
complicated kinds of traps and contrivances for excluding 
sewer air are now discarded by builders and architects for 
those simpler forms which are equally effective. 
In the matter of water-supply, the belief is steadily 
gaining ground that a water once polluted by sewage 
cannot be regarded as safe for drinking purposes. Safe | 
it may be so long as filtration on the large scale is 
efficiently performed, but any failure to thoroughly filtrate 
and aérate the water in times of epidemic visitation might 
be attended with disastrous consequences, even suppos- 
ing that filtration through sand and gravel is destructive of 
disease organisms or their spores. The introduction of a 
constant supply of water into towns, in the sense that 
cisterns and receptacles for storing water are no longer 
necessary, has been of great benefit—especially in the 
poorer parts of towns, where water stored on the premises 
is usually highly contaminated. 
Of the scientific witnesses who were examined before 
the RoyalCommission on Metropolitan Sewage Discharge, 
nearly all were in favour of the principle of separation of 
the rainfall from the sewage. ‘The rain to the river, the 
sewage to the soil.” In view of the ultimate disposal of 
the sewage, the advantages of the “separate method ” 
are very great, and would now probably lead to its 
adoption in any new scheme of sewerage for a town where 
the circumstances are favourable. From the public health 
point of view, it is also desirable to have impermeable 
pipe or brick sewers of small size, so that contamination of 
the soil by leakage into it of the contents of sewers may 
be avoided. In any such scheme of sewerage it must not 
be forgotten that not only are channels on the surfaces of 
the streets and roads required to convey away surface 
water, but pervious drains laid in the subsoil are absolutely 
necessary in the health interests of the town to keep the 
subsoil water ata permanently lowlevel. For the disposal 
of the sewage, the value of a regular daily flow, and the 
elimination of the necessity in times of heavy rain of 
dealing with an enormous and uncontrollable volume of 
dilute sewage, must be obvious. The surface waters of 
towns are certainly not clean, but where the streets are 
efficiently scavenged they are free from taint of human 
excretal refuse, and fit for admission into the rivers which 
nature intended as drainage channels of the surrounding 
high lands. 
The extreme importance of thoroughly ventilating 
sewers, Is now very generally understood. Pipe sewers 
require as much ventilation as brick sewers, although the 
absence of deposit on the smooth internal surfaces of the 
pipes, and their consequent freedom from smell due to 
decomposition of deposited organic detritus, originally led 
to the belief that ventilating openings were not required 
in pipe systems of sewerage. It was not until Dr. 
Buchanan showed in the case of Croydon that the absence 
of proper ventilation in the pipe sewers of that town was 
in all probability instrumental in aiding the spread of 
enteric fever that the opinion of engineers on this matter 
underwent a change. Displacement of air in pipe sewers 
of small diameter is greatly more sudden than in brick 
sewers of larger diameter, and it is plain, says Dr. 
Buchanan, that ‘‘means of such ventilation are wanted 
more numerously in proportion as the displacements of 
air may be local and sudden.” Openings into sewers 
from the street level are still regarded as the best 
practicable means for the admission of fresh air, and the 
exit of sewer air. Charcoal trays, Archimedean screws, and 
other contrivances for purifying the issuing air, or hasten- 
ing its exit, are now generally abandoned as useless and 
inconvenient. 
The purification and utilisation of the sewage of towns 
is a subject of much importance both in its public health 
and commercial aspects. The idea, so long entertained, 
that town sewage could by various methods be made to 
yield a manure which would give rise by its sale to an 
enormous profit is now exploded. The highest degree of 
purification, we now know, can only be attained on land 
naturally suitable from its porosity and other properties, 
and artificially prepared by extensive under-drainage. 
The agents which purify sewage in its passage through 
soil, by converting the nitrogenised organic matters into 
inorganic salts—nitrates and nitrites of the alkaline and 
earthy bases, and ammonia—have been discovered to 
be Bacterial micro-organisms, resident chiefly in the 
superficial 18 inches of soil, and far more abundant in 
some soils than in others. Sewage farming has been 
ascertained to be profitable, under suitable conditions. 
The sewage must flow from the town to the farm by 
gravitation—the cost of pumping will neutralise profits 
from the sale of farm produce ; a part of the farm must 
be laid out as a filter bed, so that the sewage, when not 
required on the cultivated land or when so dilute from the 
presence of storm waters as to be inapplicable, may be 
purified on a small very porous area by the process of 
intermittent downward filtration. Very few growing crops 
are benefited by the application of sewage, except the 
various kinds of grasses, and of these such enormous 
quantities can be produced that, unless converted into 
“silage,” or utilised on the farm in the production of 
stock and dairy produce, they may be expected to result 
in a loss, from the absence of any demand for such large 
quantities at all periods of the year. 
In this country, the sewage farm at Birmingham is 
probably the best example of what has been done to solve 
a most difficult problem by the application of sewage to 
land. Here, the sewage is first freed from its suspended 
matters by a process of precipitation, a proceeding 
necessary not only to prevent warping of the land with 
offensive solid matters, but also to withdraw the metallic 
salts and acids incidental to the sewage of a manufactur- 
ing town, which would be injurious to vegetation. Even 
this magnificent example of dealing satisfactorily with the — 
most difficult municipal problem of modern timesis eclipsed 
Pw). eww ay .- Ger ee ey tee roe eur ae eS 
