OcTOBER 30, 1902] 
prevent smoke by penal legislation, but to encourage the inter- 
ception of smoke and the removal of the sooty particles before 
the air is allowed to escape, and I will subsequently call attention 
to the share which a local authority could fairly take in such an 
enterprise. I do not say that this is the only or the best mode 
of dealing with the question; I only consider whether it is, 
prima facie, practicable enough to justify our including inquiries 
with regard to it in the demands that sanitation may reasonably 
make upon science. I offer a few considerations in mitigation 
of criticism of this venturesome proceeding. 
First, I am only practically recalling a suggestion made many 
years ago. A proposal for the treatment of smoke by the 
erection of municipal chimneys was made in Manchester by 
Mr. Peter Spence (Proceedings Manchester Lit. and Phil. Soc., 
1857). It is precisely in such a city as Manchester—a city of 
fogs and smoke, but also the city of Dalton and of Joule— 
where the facilities for the association of scientific experiments 
with real practical life have been so wonderfully developed that 
an enterprise of this character could be taken in hand. 
Secondly, the present method of dealing with smoke is by no 
means final, although, as I have said, it has marked a most 
important stage of progress. One of the most conspicuous 
features of London architecture is the enormous variety of 
smoke cowls, in all stages of dilapidation, to be seen surmount- 
ing the roofs. Almost every chimney stack is a sort of museum 
of contrivances for improving the action of chimneys. The 
mere exhibition of so many contrivances can only mean that 
smoky chimneys are not by any means so rare as they might be 
under more favourable mechanical conditions. On that very 
account, if on no other, the separate chimney method of dealing 
with smoke is not suited to the circumstances of large towns. 
Thirdly, the designer of a factory takes a further step in 
advance in the treatment of smoke, and provides a single smoke 
stack for a considerable number of independent fires. The 
separate opening of each chimney of the domestic house 
into free air is, therefore, not absolutely required for the removal 
of smoke. The factory builder is not always successful in using 
his chimney for preventing smoke, but he is successful in leading 
the foul air of many flues into one channel which might afford 
an opportunity for depriving the smoke of its soot. 
Moreover, arrangements for propelling air mechanically are 
becoming every day more extended. Some of them as em- 
ployed in various systems of ventilation are quite as elaborate 
as any that would be required to deal with the smoke of an 
ordinary house or block of houses. There is no sufficient 
distinction to be drawn between coal smoke and other forms of 
refuse that foul the air to make it necessary to use one system 
for the former and a different one for the others. It thus seems 
almost certain that if the domestic architect had sufficient en- 
couragement to make the attempt, he would not find the plan 
of dealing with household smoke by the method of the factory 
chimney or by mechanical propulsion beyond the range of 
practical physics. 
Some Particulars of the Smoke Problem. 
For purposes of comparison, I next consider what is the 
amount of smoke-laden air with which we have to deal. It is 
difficult to give any but the roughest estimate. I assume that 
on the average every house of the 600,000 rated for the 
municipal purposes of London has two fires burning, and there- 
fore two chimneys emitting smoky air, for twelve hours each 
day, and that each chimney uses and defiles 10,000 cubic feet 
of air per hour. If these estimates are inaccurate, we can at 
least ask scientific men to correct them. On these assumptions, 
every “‘ working chimney” delivers 4°2 tons of smoky air per 
day ; every house, on the average, 8'4 tons. We thus obtain 
the estimate of five millions of tons of smoky air sent up the 
household chimneys of London in one day. Allowing for the 
14,500 factories of London, which are not altogether innocent 
in the matter of smoke, as equivalent each to thirty house 
chimneys, we get an additional two million tons of air fouled 
with smoke ; that is, in the aggregate about seven million tons 
of air are used per day in London to carry away smoke! as 
compared with about a million tons of water to carry away 
1 A layer of air 60 feet thick over the 75,000 acres comprised within the 
administrative county of London would weigh about 7,000,000 tons. The 
calculation suggests that on a day of dense fog, when there is very little 
horizontal movement of air, there is a more or less complete circulation of 
the air through the chimneys and back again to the streets and houses 
during the hours when chimneys are active. Dr. W. J. Russell's analyses 
of air during fog lend support to this suggestion. 
NO. 1722, VOL. 66] 
NATURE 
669 
sewage. The cost of dealing with the sewage is about 600/. 
per day. Supposing that a ton of dirty air could be ‘‘ treated” 
for the same cost as a ton of sewage, the cost of clearing the 
air of London might be set down at 4200/. a day, equivalent to 
to a rate of rod. in the pound. 
To move airis acomparatively cheap matter. An electrically- 
driven fan will do the day’s work of a single chimney, as regards 
smoky air, at a cost of about a penny, under suitable conditions. 
A single colliery fan has been made to deliver as much as 
200,000 cubic feet of air per minute, and its output therefore 
amounts to about 10,000 tons a day, or sufficient to carry the 
smoke of more than 1000 London houses on the scale mentioned 
above. Five hundred of such fans would carry the household 
smoke of the whole of London. It would mean a huge aggre- 
gation of power, but London means the same. 
These figures show that although the volume of smoky air is 
vastly larger than the volume of sewage, yet the cost of dealing 
with it for the purpose of treatment may not be of an altogether 
different order of magnitude from the cost of the manipulation 
of London sewage, and the point at which I wish to arrive is, 
that we are justified in asking practical men of science, as a first 
question, whether the treatment of smoky air, on a plan some- 
what similar to the treatment of sewage, is mechanically possible 
within reasonable limits of original outlay and current expense. 
Limitation of the Analogy. 
Beyond this point it would be necessary to diverge in the 
treatment of smoke from the plan adopted with sewage, both as 
regards the special method of dealing with it and as to the part 
which the local authorities should take in encouraging ands 
assisting the purification of air. 
I do not suppose that it is possible to establish a few maim. 
drains for smoky air corresponding to the main sewage drains, 
and to use one or two cleansing stations for purifying the air 
from smoke ; but it might be possible to achieve a similar result 
by a large number of systems on a correspondingly small scale, 
and the systems might be some of them municipal and some 
private. A single block of houses might have means for drawing 
off the smoke from all its fires intoa chamber wherein the smoke 
could be treated, before the fouled air was allowed to pass into 
the atmosphere, and if such a system were mechanically feasible 
we should then beable to put a second question to practical men 
of science, viz., whether it is not possible completely to deposit 
from the air as it passes on its way the solid particles which 
form the smoke. It has been shown that sooty particles 
coagulate under mechanical action, and some years ago Sir 
Oliver Lodge showed experiments on the deposition of smoke 
in a closed chamber by means of electricity. I should now like 
to ask whether it is not possible to make a further advance in 
this direction. I do not demand that no smoke shall be pro- 
duced. I think that people may prefer to pay the cost of 
abstracting the smoke if they enjoy the free use of open fires, to 
which, in England, we are so much attached. 
The Question of Cost. 
If men of science give us satisfactory answers as to the 
physical possibilities, the question then becomes one of cost. 
Suppose that the cost amounts to the equivalent of a tenpenny 
rate. Would ratepayers be willing to expend a sum of that 
magnitude for the purpose of eliminating smoke from the 
atmosphere of London or Manchester ? 
In considering this aspect of the question, it should be re- 
membered that the result, if successful, would have some 
economies to set down per contra. 
A bad fog in London, according to the Z%es, may cost 
5000/. a day for additional gas alone; to that we have to add 
the loss due to interference with traffic and other incidental items, 
I have seen the cost of a day’s fog estimated variously at from 
20,000/, to 50,000/., and the cost per annum is set, I think by 
Mr. Rollo Russell, at from three to five million pounds, If any 
of these estimates be true, the equivalent of a tenpenny rate 
would obviously be a very cheap substitute for the smoke of 
London. Certainly, whatever may be the materiai damage of 
a day’s fog, the moral and intellectual damage should be 
reckoned as no inconsiderable addition, and if the indirect results 
of the dirt of London smoke could be avoided, even an additional 
tenpenny rate might be found acceptable to a majority of rate- 
payers. 
1 The plan of using a single chinney for a building comprising a chemical 
laboratory and suite of offices—sixteen rooms—has been carried out at the 
Manchester Alum Works in pursuance of Mr. P. Spence’s idea. 
