Whatever opinions may be formed of the merits of the exhibits at South
Kensington, one result is unquestionable—the exhibition itself has
done much in directing public attention to the very important subject
of economizing fuel and the diminution of smoke. We sorely need some
lessons. Our national progress in this direction has been simply
contemptible, so far as domestic fireplaces are concerned.
To prove this we need only turn back to the essays of Benjamin
Thompson, Count of Rumford, published in London just eighty years
ago, and find therein nearly all that the Smoke Abatement Exhibition
_ought_ to teach us, both in theory and practice—lessons which all our
progress since 1802, plus the best exhibits at South Kensington, we
have yet to learn.
This small progress in domestic heating is the more remarkable when
contrasted with the great strides we have made in the construction and
working of engineering and metallurgical furnaces, the most important
of which is displayed in the Siemens regenerative furnace. A climax
to this contrast is afforded by a speech made by Dr. Siemens himself,
in which he defends our domestic barbarisms with all the conservative
inconvincibility of a born and bred Englishman, in spite of his German
nationality.
The speech to which I refer is reported in the “Journal of the Society
of Arts,” December 9, 1881, and contains some curious fallacies,
probably due to its extemporaneous character; but as they have been
quoted and adopted not only in political and literary journals, but
also by a magazine of such high scientific standing as _Nature_ (see
editorial article January 5, 1882, p. 219), they are likely to mislead
many.
Having already, in my “History of Modern Invention, etc.,” and in other
places, expressed my great respect for Dr. Siemens and his benefactions
to British industry, the spirit in which the following plain-spoken
criticism is made will not, I hope, be misunderstood either by the
readers of “Knowledge” or by Dr. Siemens himself.
I may further add that I am animated by a deadly hatred of our
barbarous practice of wasting precious coal by burning it in iron
fire-baskets half buried in holes within brick walls, and under
shafts that carry 80 or 90 per cent of its heat to the clouds; that
pollute the atmosphere of our towns, and make all their architecture
hideous; that render scientific and efficient ventilation of our houses
impossible; that promote rheumatism, neuralgia, chilblains, pulmonary
diseases, bronchitis, and all the other “ills that flesh is heir to”
when roasted on one side and cold-blasted on the other; that I am so
rabid on this subject, that if Dr. Siemens, Sir F. Bramwell, and all
others who defend this English abomination, were giant windmills in
full rotation, I would emulate the valor of my chivalric predecessor,
whatever might be the personal consequences.
Dr. Siemens stated that the open fireplace “communicates absolutely no
heat to the air of the room, because air, being a perfectly transparent
medium, the rays of heat pass clean through it.”
Here is an initial mistake. It is true that air which has been
artificially deprived of _all_ its aqueous vapor is thus completely
permeable by heat rays, but such is far from being the case with
the water it contains. This absorbs a notable amount even of bright
solar rays, and a far greater proportion of the heat rays from a
comparatively obscure source, such as the red-hot coals and flame of a
common fire. Tyndall has proved that 8 to 10 per cent of all the heat
radiating from such a source as a common fire is absorbed in passing
through only 5 feet of air in its ordinary condition, the variation
depending upon its degree of saturation with aqueous vapor.
Starting with the erroneous assumption that the rays of heat pass
“clean through” the air of the room, Dr. Siemens went on to say that
the open fireplace “gives heat only by heating the walls, ceiling, and
furniture, and here is the great advantage of the open fire;” and,
further, that “if the air in the room were hotter than the walls,
condensation would take place on them, and mildew and fermentation of
various kinds would be engendered; whereas, if the air were cooler than
the walls, the latter must be absolutely dry.”
Upon these assumptions, Dr. Siemens condemns steam-pipes and stoves,
hot-air pipes, and all other methods of directly heating the _air_
of apartments, and thereby making it warmer than were the walls, the
ceiling, and furniture when the process of warming commenced. It is
quite true that stoves, stove-pipes, hot-air pipes, steam-pipes,
etc., do this; they raise the temperature of the air directly by
_convection_, _i.e._, by warming the film of air in contact with their
surfaces, which film, thus heated and expanded, rises towards the
ceiling, and, on its way, warms the air around it, and then is followed
by other similarly-heated ascending films. When we make a hole in the
wall, and burn our coals within such cavity, this convection proceeds
up the chimney in company with the smoke.
But is Dr. Siemens right in saying that the air of a room, raised by
convection above its original temperature, and above that of the walls,
deposits any of its moisture on these walls? I have no hesitation in
saying very positively that he is clearly and demonstrably wrong; that
no such condensation can possibly take place under the circumstances.
Suppose, for illustration sake, that we start with a room of which the
air and walls are at the freezing point, 32° F., before artificial
heating (any other temperature will do), and, to give Dr. Siemens every
advantage, we will further suppose that the air is fully saturated
with aqueous vapor, _i.e._, just in the condition at which some of its
water might be condensed. Such condensation, however, can only take
place by cooling the air _below_ 32°, and unless the walls or ceiling
or furniture are capable of doing this they cannot receive any moisture
due to such condensation, or, in other words, they must fall below
32° in order to obtain it by cooling the film in contact with them.
Of course Dr. Siemens will not assert that the stoves or steam-pipes
(enclosing the steam, of course), or the hot-air or hot-water pipes,
will lower the _absolute_ temperature of the walls by heating the air
in the room.
But if the air is heated more rapidly than are the walls, etc., the
_relative_ temperature of these will be lower. Will condensation of
moisture _then_ follow, as Dr. Siemens affirms? Let us suppose that
the air of the room is raised from 30° to 50° _by convection purely_;
reference to tables based on the researches of Regnault, shows that at
32° the quantity of vapor required to saturate the air is sufficient to
support a column of 0·182 inch of mercury, while at 50° it amounts to
0·361, or nearly double. Thus the air, instead of being in a condition
of giving away its moisture to the walls, has become thirsty, or in a
condition to _take moisture away from them_ if they are at all damp.
This is the case whether the walls remain at 32° or are raised to any
higher temperature short of that of the air.
Thus the action of close stoves and of hot surfaces or pipes of any
kind is exactly the opposite of that attributed to them by Dr. Siemens.
They dry the air, they dry the walls, they dry the ceiling, they dry
the furniture and everything else in the house.
In _our_ climate, especially in the infamous jerry-built houses of
suburban London, this is a great advantage. Dr. Siemens states his
American experience, and denounces such heating by convection because
the close stoves _there_ made him uncomfortable. This was due to the
fact that the winter atmosphere of the United States is very dry, even
when at zero. But air, when raised from 0° to 60°, acquires about
twelve times its original capacity for water. The air thus simply
heated is desiccated, and it desiccates everything in contact with it,
especially the human body. The lank and shriveled aspect of the typical
Yankee is, I believe, due to this. He is a desiccated Englishman, and
we should all grow like him if our climate were as dry as his.[30] The
great fires that devastate the cities of the United States appear to
me to be due to this general desiccation of all building materials,
rendering them readily inflammable and the flames difficult of
extinction.
When an undesiccated Englishman, or a German endowed with a wholesome
John Bull rotundity, is exposed to this superdried air, he is subjected
to an amount of bodily evaporation that must be perceptible and
unpleasant. The disagreeable sensation experienced by Dr. Siemens in
the stove-heated railway cars, etc., were probably due to this.
An English house, enveloped in a foggy atmosphere, and encased in
damp surroundings, especially requires stove-heating, and the most
inveterate worshipers of our national domestic fetish, the open grate,
invariably prefer a stove or hot-pipe-heated room, when they are
unconscious of the source of heat, and their prejudice hoodwinked.
I have observed this continually, and have often been amused at the
inconsistency thus displayed. For example, one evening I had a warm
contest with a lady, who repeated the usual praises of a cheerful
blaze, etc., etc. On calling afterwards, on a bitter snowy morning, I
found her and her daughters sitting at work in the billiard-room, and
asked them why. “Because it is so warm and comfortable.” This room was
heated by an eight-inch steam-pipe, running around and under the table,
to prevent the undue cooling of the indiarubber cushions, and thus the
room was warmed from the middle, and equally and moderately throughout.
The large reception-room, with blazing fire, was scorching on one side,
and freezing on the other, at that time in the morning.
The permeability of ill-constructed iron stoves to poisonous carbonic
oxide, which riddles through red-hot iron, is a real evil, but easily
obviated by proper lining, The frizzling of particles of organic
matter, of which we hear so much, is—if it really does occur—highly
advantageous, seeing that it must destroy organic poison-germs.
Under some conditions, the warm air of a room _does_ deposit moisture
on its cooler walls. This happens in churches, concert-rooms, etc.,
when they are but occasionally used in winter time, and mainly warmed
by animal heat, by congregational emanations of breath-vapor, and
perspiration—_i.e._, with warm air supersaturated with vapor. Also,
when we have a sudden change from dry, frosty weather to warm and
humid. Then our walls may be streaming with condensed water. Such cases
were probably in the mind of Dr. Siemens when he spoke; but they are
quite different from stove-heating or pipe-heating, which increase
the vapor capacity of the heated air, without supplying the demand it
creates.