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substituted for the older system the method of disposal by fire, and in London the City Commissioners
of Sewers, the District Board of Whitechapel, the Vestry of Battersea, the Vestry of Hampstead
and the Woolwich Local Board have erected destructors, while several other sanitary authorities within
the county are contemplating doing so.
With a view to ascertaining the experience of medical officers of health in whose districts
destructors have been erected with regard to complaints of nuisance, a circular letter of inquiry has
been sent out, and the replies which have been received are tabulated in Appendix iii.
A point to be borne in mind in giving due weight to the presence or absence of complaints with
regard to any particular destructor is the character of the neighbourhood in which it is situated. The
cost of leading the refuse to the depot has determined in most instances that the destructor shall be in
a fairly central situation. A reference to the appendix will show that in many cases there are inhabited
houses in close contiguity to it. This is not perhaps a matter of such importance as might at first sight
appear, for provided that the chimney shaft be sufficiently high, experience shows that if complaints of
nuisance are received they do not proceed from inhabitants in the immediate vicinity, but from those
who live at some considerable distance from the depot. No doubt, other things being equal, exception
is least likely to be taken to a destructor situated in the centre of a manufacturing district, and
it should be remembered that when a depot is thus placed, it is possible that the absence of complaints
of nuisance is in part attributable to this cause, and such absence does not necessarily imply that the
means adopted for preventing nuisance are altogether worthy of imitation.
An examination of the replies tabulated in the appendix will show that continued complaints of
smell or dust have not been forthcoming in the majority of instances, and complaints that manufacturing
processes have been deleteriously affected by the destructor are still more infrequent. In several instances
we were informed that there was much local opposition to the establishment of a destructor when the
scheme was in contemplation, and in some cases complaints of dust and smoke seem to have come to
hand before any refuse was burnt in the furnaces.
It is a much more difficult matter than might at first sight appear to localise and trace to its
source a given nuisance, and it is quite possible that in some instances the destructor has been
accused of producing a smell which was really attributable to some other cause. The manager of a
gas factory who complained that the neighbouring destructor brought the gas works into discredit
is certainly to be complimented on his ingenuity.
Nuisance from dust stands on a somewhat different footing, and hence the complaint of the
proprietor of a vinery, and the complaint which we were told was received from a sugar manufactory,
would appear to constitute a serious charge against the destructors concerned. The complaints with
respect to pieces of charred paper are of quite unmistakeable importance.
The most interesting information given in the appendix, is that which relates to the means
which the several medical officers of health believe to have been effectual in doing away with or
minimising nuisance.
In one case there is an absolute confession of failure, it being "intended to remove the
destructor to the sewage works, where it will be at some distance from inhabited houses." In a few
instances a grid or screen has been placed in the flue, this of course implies the admission that the
combustion in the furnace is far from complete. Some of the replies state that benefit has accrued
from an improved system of firing. Six medical officers of health are of opinion that Jones'
Fume Cremator is effectual in minimising or securing the complete removal of any cause of offence;
two state that cremators form part of the destructor plant, but that they are not used; another
medical officer of health is not satisfied with Jones' cremator; three attach importance to the use of
the forced blast produced by steam jets, and one thinks it desirable that the unburnt refuse should not
be heated before combustion.
Our own observation has led us to attach special importance to the two points last named. In
our opinion any arrangement which makes it possible for the imperfectly heated gases from drying
refuse to escape into the flue without being compelled to pass through the hottest part of the furnace,
is an imperfect one. It is true that such gases may be completely burnt by subsequent exposure to
the heat of a cremator, but the most satisfactory and economical method appears to be to secure the
most complete combustion possible in the cell itself.
We regard the use of forced draught as a most effective means of preventing nuisance. We
have already alluded to the temperatures in the flues at Leeds. Dr. Spottiswoode Cameron, the Medical
Officer of Health of that city, gives in his annual report for 1891 the results of some experiments of
considerable interest. A comparison was made between the temperatures registered in the Kidacrestreet
destructors with and without the use of the steam jets. The pyrometers were placed in each
instance in the side flues between the furnaces, and the average of 24 observations without steam jets
was 1118° Fahr., and the average of 21 observations with steam jets was 1464° Fahr. Dr. Cameron
writes, "The observed temperatures with the jets were 346° Fahr., above those without, but taking
into account the fact that upon 17 occasions in the one case against 3 in the other the temperature
was too high to be registered, the real difference would be nearer 500° Fahr."
At Oldham a series of experiments by the Messrs. Watson, based on the principle of the method
of mixtures showed that the average temperature of the mattrass chamber through which the hot gases
pass on their way to the boiler was 2019° Fahr., the minimum being 1654° Fahr., and the maximum
2346° Fahr.
The use of the steam jet is said to prolong the life of the fire bars; on the other hand, it has been
objected to on account of the noise which it produces, and it does not appear to be capable of application
to all forms of cell. At Hornsey, where the exit flues are at the back of the furnace, close to the
feed hoppers, we were told that its use had to be discontinued, as it led to firing of the refuse in the
hoppers.
The amount of heat to which a given portion of refuse is subjected is determined by two factors,
the temperature and the duration of exposure The latter is only a very short period in the case of