gether with Remarks and Obfervations on their
Refults, and on the Improvements that may be de
rived from them. An Account of feme Experi
ments made on a very large Scale in a Brew-houfc
Boiler. An Account of a Brew-houfe Boiler con-
ftr ufted and fitted up on an improved Plan.
Refults of feveral Experiments which were made
with this new Boiler. Of the Advantage in re
gard to the Economy of Fuel in boiling Liquids^
which arifes from performing that Procefs on a
large Scale. Thefe Advantages are limited*
An Account of an Alteration which was made, in
the new Brew-houfe Boiler^ with a view to the
SAVING OF TIME in caujing its Contents to boiL
Experiments Jhowing the Effects produced by
thefe Alterations. An EJl'maie of the RELATIVE
QUANTITIES OF HEAT producible from COAKS
PIT^COAL CHARCOAL, and OAK. A Me
thod of ejtimating the Quantity of Pit-coal which
would be nccejjary to perform any of the Proceffes
mentioned in this EJJay^ in which Wood was ufed
as Fuel. An Eftimate of the TOTAL QUANTI
TIES of Heat producible in the Combuftion of dif
ferent Kinds of Fuel ; and of the real Quantities of
Heat
76 Of the Management of Fire,
Heat which are Ay?, under various Circumjlances^
in culinary Proceffes.
WHAT has been faid in the foregoing Chapter
will, I truft, be fufficient to give my reader
a clear and diftinct idea of the fubject under con-
fideration, in all its various details and connex
ions, and enable him to comprehend, without
the fmalleft difficulty, every thing I have to add
on this fubject ; and particularly to difcover the
different objects I had in view in the Experiments
of which I am now about to give an account, and
to judge with facility and certainty of the conclu*
fions I have drawn from their refults.
Thefe Experiments, though they occupy fo many
pages in this Effay., are but a fmall part of thofe I
have macb, and caufed to be made under my di
rection, on the fubject of Heat, during the laft
feven years. Were I to publifh them all, with all
their details as they are recorded in the regifter that
has been kept of them, they would fill feyeral
volumes.
It was inoft fortunate for me that this regifter is
very voluminous ; for had it not been fo, I Ihould
in all probability have taken it with me to England
laft year, and in that cafe I Ihould have loft it,
with the reft of my papers, in the trunk of which
I was robbed in pafiing through St. Paul's church
yard, on my arrival in London after an abfence of
eleven years. *
As
* I have many rcafons to think that thcfe papers arc ftill in being ;-
what an everhfting obligatien ihould I be under to the perfon who
would caufe them to be returned to me }
and the Economy of Fitch 77
As I forefaw, when I firft began my inquiries
refpeding Heat, that I ihould have occafion to
make many experiments on boiling Liquids, to
facilitate the regiftering of them I formed a Table,
(which I had printed) in which, under various
heads, every circumftance relative to any common
Experiment of the kind in queftion could be en
tered with much regularity, and with little trouble.
As this Table may be ufeful to others who may
be engaged in fimilar purfuits, and as the publiih-
ing of it will alib tend to give my reader a more
perfect idea of the manner in which my Experi
ments were conducted, I fhall (as an example) give
an account of one Experiment, in the fame form in
which it was regiftered in one of thefe printed
Tables.
Thefe Tables, as they are printed for ufe, (on de
tached iheets) occupy one fide of half a flieet of
common folio writing-paper.
?s
Of the Management of Fire y
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and the Economy of Fuel. 79
Every thing in this Table, except fuch figures
and words as are printed between crochet
is contained in the printed forms : Hence it i
evident how much thefe Tables tend to diminifli
the trouble "of regiftering the refults of Ixperi-
ments of this kind, and alfo to prevent miftab
The example I have here given is an account of
an Experiment, in which a very large quantity of
water, equal to 15,590 Ibs. Avoirdupois in weight,
or 1866 wine gallons of 231 cubic inches each; but
it is evident that thefe Tables anfwer equally well
for the fmall quantity contained by the fmalleft
faucepan.
The height of the barometer is expreffed in Pans
inches ; that of the thermometer in degrees of
Fahrenheit's fcale. The other meafures, as well
of length as of capacity, are the common meafures
of the country (Bavaria ;) and the weight is ex-
preffed in Bavarian pounds, of which 100 make
1 23.84 Ibs. Avoirdupois.
What is entered under the head of GENERAL
RESULTS OF THE EXPERIMENT, requires no ex-
planation ; but what I have called the PRECISE
RESULT muftbe explained.
Having frequent occafion to compare the refults
of Experiments made at different times and in dif
ferent feafons of the year, as the temperature of the
water in the Boiler when the fire is lighted under it
is feldom the fame in any two Experiments, and as
the boiling heat varies with the variations of the
preffure of the atmofphere, or of the height of the
mercury
8 o Of the Management of Fire^
mercury in the barometer, it became neceffary to
make proper allowances for thefe differences. This
I thought could beft be done by determining, by
computation, from 'the number of degrees the
water was actually heated, and the quantity of Fuel
confumed in heating it that number of degrees,
how much Fuel would have been required to have
if heated 1 80 degrees, or from the point of freezing
to that of boiling water (the boiling point being
taken equal to the temperature indicated by 212
of Fahrenheit's thermometer, which is the boiling
point under the mean preffure of the atmofphere
at the furface of the fea) : Then, by dividing the
weight of the water ufed in the Experiment, (ex-
preffed in pounds) by the weight of the Fuel cx-
preffed in pounds neceffary to heat it 180 degrees,
or from the temperature of freezing to that of
boiling water ; this gives the number of pounds of
ice-cold water which (according to the refult of the
given Experiment) might have been made to boil,
with the heat generated in the combuftion of i Ib,
of the Fuel, under the mean preffure of the at
mofphere at the level of the furface of the fea.
The city of Munich, where all the Experiments
were made of which I am about to give an account,
being fituated almoft in the centre of Germany,
lies very high above the level of the fea. The
mean height of the mercury in the barometer is
only about 28 Englifli inches, confequently water
boils at Munich at a lower temperature than at
London. The difference is even too considerable
to
and the Economy of FiteL 8 1
to be neglected, it amounts to 2^ degrees of Fah
renheit's fcale, being 2097 degrees at a medium
at Munich, and 212 degrees in all places fituated
near the level of the fea. To render the refults of
my experiments and computations more fimple and
more generally ufeful, I mall always make due
allowance for this difference.
Having, from the aftual refutt of each Expert-
ment, made a computation on the principles hers
defcribed, mowing what (for the want of a better
expreffion) I have called the Pretifs Refult of the
Experiment, it is evident that thefe computations
mow very accurately the comparative merit of the
mechanical arrangements, and the management of
the Fire in condufting the Experiments, in as far
as relates to the Economy of Fuel 5 for the more
ice-cold water that can be made to boil with ^ the
heat generated in the combuflion of any given
quantity (i Ib- for inilance) of Fuel, the morei
perfect of courfe (other things being equal) muft
be the conftruction of the fire-place.
Under the head of PRECISE RESULT* I have
fometimes added another computation, mowing
how much " boiling-hot water" might, according to
the refult of the given Experiment* be kept boiling
" one hour" with the heat generated in the combui-
tion of i Ib. of the Fuel." Though I have called
this a Precife Refult, it is evident that in moft cafes
it cannot be confidered as being very exact, owing
to the difficulty of eftimating the quantity of Fuel
in the fire-place, which is wiconfumed at the moment
when the water begins to boil-
VOL. II M fo
82 Of the Management of Fire y
In the foregoing example, in making this com
putation I fuppofed that, when the water began to
boil, there was wood enough in the fire-place un-
conf timed to keep the water boiling 43 minutes,
and that the wood added afterwards ( i oo Ib.) kept
the water boiling the remainder of the time it boil-
$, or juft 2 hours.
In moft cafes, however, to fave trouble in mak
ing thefe computations, I have fuppofed that all
the wood employed in making the water boil is en
tirely confumed in that procefs, and that all the
lieat expended in keeping the water boiling is fur-
nifhed by the Fuel which is added after the water
bad begun to boll. This fuppoiition is evidently
erroneous ; but as the computation in queftion can
at beft give but an inaccurate and doubtful refult,
labour beftowed on it would be thrown away :
But imperfect as thefe rough eflimatcs are, they
will however in many cafes be found ufeful.
In giving an account of the following Experi
ments, I mall not place them exactly in the order in
which they were made, but mall arrange them in
fuch a manner as I mall think beft, in order that;
the information derived from their refults may
appear in a clear point of view.
For greater convenience in referring to them.,
I ihaU number them all ; and as I have already
given numbers to the four I mentioned in the Firft
Chapter of this Eflay, I mall proceed in regular
order with the reft.
'and tie Economy of Fuel. 83
Experiment, No. 5.
The firft kitchen of the Houfe of Induftry at
Munich has already been defcribed in the Firft
Chapter of this Effay ; and it was there- mentioned,
that the daily expenfe of Fuel in that kitchen,
when food (peas-foup) was prepared for i ooo per-
fons, amounted to 300 Ib. in weight of dry beech-
wood. Now as each portion of foup coniifted of
i Ib. this gives 0.3 of a pound of wood for each
pound of foup.
Experiment, No. 6.
The firft kitchen of the Houfe of Induftry hav
ing been pulled down, it was afterwards rebuilt on
a different principle. Inftead of Copper Boilers,
Iron Boilers of a herru'fpherical form were now
ufod, and each of thefe Boilers had its own feparate
clofed fire-place. The Boiler being fufpended by
its rim in the brick-work, and room being left for
the flame to play all round it. The fmoke went
off" into the chimney by an horizontal canal, 5
inches wide and 5 inches high, which was con
cealed in the mafs of brick-work, and which open
ed into the fire-place on the fide oppofite to the
opening by which the Fuel was introduced.
The Fire was made on a flat iron grate placed
directly under the Boiler, and diftant from its bot
tom about 1 2 inches. The afh-pit door was fur-
niflied
84 Of the Management of Ftre^
nifhed with a regifter ; but there was no damper
to the canal by which the fmoke went off into the
chimney, which was a very great defeft. The
opening into the fire-place was clofed by an iron
door. Each of thefe Iron Boilers weighed about
148 Ibs. Avoirdupois, was 25^ Englifli inches in
diameter, and 14*935 mcnes deep, and contained
190^- Ibs. Bavarian weight of water, equal to
235.91 Ibs. Avoirdupois, or about 28- Englifli
wine-gallons.
From this account of the manner in which thefe
Iron Boilers were fitted up, it is evident that the
arrangement was not effentially different from that
of kitchens for hofpjtals, as they are commonly
conftru&ed.
From Experiments made with care, and often
repeated, I found that to prepare 89 portions (or
89 Ibs. Bavarian weight) ofpeas-foup in one of
thefe Boilers, 43 Ibs. of dry beech-wood were re
quired as Fuel, and that the procefs lafted four
hours and an half: This gives 0.483 of a pound
of wood for each pound of the foup.
In the fir ft arrangement of this kitchen, only
0,3 of a pound of wood was required to prepare
i Ib. of foup j Hence it appears that the kitchen
had not been improved, confidered with a view
to the Economy of Fuel, by the alterations which
had been made in it. This was what I expefted ;
for the object I had in view in conftrucling this
kitchen was not to fave Fuel, but to find out
Jiow much of it is wafted in culinary procefles, a^
they
and the Economy of Fuel. 85
they a^c commonly performed on a, large fcale in
hofpitakand other institutions of public charity.
Till I knew; this, it was not in my power to eftimate,
with any degree of precifion, the advantages of any
improvements I might introduce in the conilruclion
of kitchen fire-places.
To determine in how far the quantity of Fuel
neceflary in any given culinary procefs depends on
the form of the fire-place, (the Boiler and every
other circumflance remaining the fame) I made
the following Experiments.
Experiments, No. 7 and No. 8.
Two of the Iron Boilers in the kitchen of the
Houfe of Induftry (which, as they were both call
from the fame model, were as near alike as poilible)
being chofen for this Experiment, one of them
(No- 8.) being taken out of the brick-work, its
fire-place was altered and fitted up anew on im
proved principles. The grate was made circular
and concave, and its diameter was reduced to 1 2
inches ; the' fire-place was made cylindrical above
the grate, and only 1 2 inches in diameter ; and
the Boiler being feated on the top of the wall of
this cylindrical fire-place, the flame palling through
a fmall opening on one fide of the fire-place, at the
top of it, made one complete turn about the Boiler
before it was permitted to go off into the canal by
which the fmoke paffed off into the chimney.
Though
86" Of the Management of Fire,
Though there was no damper in this canal,
yet as its entrance or opening, where it joined the
canal which went round the Boiler, was confider-
ably reduced iu fize s this anfwered (though im
perfectly) the purpofe of a damper. This fire
place being completed, and a fmall Fire having
been kept up in it for feveral days to dry the ma-
fonry, the Experiment was made by preparing thg
fame quantity of the fame kind of foup in this, and
in a neighbouring Boiler whofe fire-place had not
been altered.
The food cooked in each was 89 Ib. of Peas-
foup ; and the Experiment was begun and finifhed
in both Boilers at the fame time.
The wood employed as Fuel was pine ; and it
had been thoroughly dried in an oven the day be
fore it was ufed.
The Boilers were both kept conftantly covered
with their double covers, except only when the
Soup was ftirred about to prevent its burning t<3
the bottoms of the Boilers.
The refult of this interefling Experiment was as
follows :
Quantity of wood confumed in cook
ing 89 Ibs. Bavarian -weight of
Peas foup - - - -
Experiment
Experiment
No. 7.
No. 8.
In the Boiler
No. 8,
In the Boiler
with the im
No. I.
proved Fire
place.
37 Iks.
14 Ibs.
Thefe
and the Economy of Fuel. 87
Thefe Experiments were made on the yth of
November, 1794. On repeating them the next
day with pine-wood, which had not been previoufly
dried in an oven, the refult was as follows :
Experiments i No. 9 and No. i o.
Experiment
o. 9.
Experiment
No. 10.
In the Boiler
In the boiler
tfo. I.
No. 8,
with the im
proved File-
place.
39 Iks.
1 6 Ibs.
Quantity of wood confumed In cook-
*"" ing 3 9 Ibs. of Peas-foup - -
The firft remark I fliall make on the refults of
thefe Experiments is the proof they afford, by com
paring them with that which preceded them,
(No. 6.) of .the important fact, that pine-wood af
fords more heat in its combuftion than beech. This
fact is the more extraordinary, as it is directly con
trary to the opinion generally entertained on that
(abject ; and it is the more important, as the price
of pine-wood is, in moft places, only about half as
high as that of beech, when the quantities, eftimatcd
by weight, are equal.
In the Experiment No. 6. it was found, that
43 Ib. of dry beech-wood were neceflary, when ufed
as Fuel, to prepare 89 Ibs. of Peas-foup. In the
'Experiment No. 7. the fame procefs was per
formed with 37 Ib. and in the Experiment No. 9.
with
88 Of the Management of Fire,
with 39 Ib. of dry pine. But I (hall have occafion
to treat this fubjecl more at length in another place.
In the mean time I would, however, juft obferve ?
that all my Experiments have uniformly tended to
confirm the fact:, that dry pine-wood affords more
heat in combuflion than dry beech. I have reafon
to think the difference is in fad greater than the
Experiments before us indicate ; but the apparent
amount of it will always depend in a great meafure
on the circumftances under which the Fuel is con-
fumed ; or, in other words, on the conftruction of
the fire-place ; and it is no fmall advantage attend
ing the fire-places I mall recommend, that they are
fo contrived as to increafe, as much as it is poflible,
the fuperiority of the moft common and cheapefl
fire-wood over that which is more fcarce and
coftly.
By comparing the remits of thefe two fets of Ex-'
periments (No. 7 and No. 8, No. 9 and No. 10.)
an eftimate may be made of the advantage of ufing
very dry wood for Fuel, inftead of making ufe of
wood that has been lefs thoroughly dried ; but as I
mean to take an opportunity of inveftigating that
matter alfo more carefully hereafter, I fhall not at
prefent enlarge on it farther than juft to obferve,
that 2,3 tue wood, which was dried in an oven, was
weighed for ufe after it had been dried, and as it
certainly :d more before it was put into the
oven, the real, laving arifing from ufing it in this
dried ftate i: not fo great as the difference in the
weights of the quantities of wood ufed in the two
Experiments
and the Economy of Fuel. 89
Experiments. To eftimate that faving with precif-
jon, the wood fhoulci be weighed before it is dried,
or in the fame ftate in which the other parcel of
wood, which is uied without being dried, is
weighed,
But to. proceed to the principal objecl I had in
view in thefe Experiments ; *the determination of
the effects of the difference in the conilruction of
the two fire-places ; the difference in the quantity
of Exiel expended in the two fire-places in per
forming the fame procefs, {hows, in a manner
which does not ftand in need of any illuftration,
how much had been gained by the improvements
which had been introduced.
Conceiving it to be an objecl of great impor
tance to afcertain by aftual experiment, and with as
much precifion as poffible, the real amount of the
advantages, in regard to the Economy of Fuel, that
may be derived from improvements in the forms of
fire-places, I did not content myfelf with improv
ing from time, to time the kitchens I had con-
ftrucled, but I took pains to determine how much
I had gained by each alteration that was made,
This was neceffary, not only to furnifli myfelf with
more forcible arguments to induce others to adopt
my improvements, but alfo tp ; fatisfy myfelf with
regard to the prpgrefs I made v in my inyeftigations..
In the firft arrangement of the kitchen of the
Military Academy, the Boilers were fufpended by
their rims in the brick- work in fuch a manner that
VOL. II. N the
$0 Of the Management of Fire,
the flame could pafs freely all round them, and the
fmoke went off in horizontal canals which led^to
the chimney, but which were not furnifhed with
dampers.
The Fire was made on a flat fquare iron grate ;
and the internal diameter of the fire-place was 2 or
" inches larger than the diameter of the Boiler
which belonged to it. The bottom of the Boiler
was from 6 to 10, or 12 inches (according to its
fize) above the level of the grate ; and the door of
the opening into the fire-place, by which the Fuel
was introduced, was kept conflantly clofed. The
afli-pit door was furnifhed with a regifter, and the
Boilers were all furnifhed with double covers.
Having, in confequence of the progrefs I had
made in my inquiries refpecling the Management of
Heat, and the Economy of Fuel, come to a refolu*
tion to pull down this kitchen, and rebuild it on an
improved principle ; previous to its being demol-
ifhed, I made feveral very accurate Experiments to
determine the real expenfe of Fuel in the fire,
places as they then exijled^ with all their faults ; and
when the new arrangement of the kitchen was
completed, I repeated thefe Experiments with the
fame Boilers ; and by comparing the refults of thefe
two fets of Experiments, I was able to eftimate
with great precifion the real amount of the faving
of time as well as of Fuel, which were derived
from the improvements I had introduced.
After all that has been faid (and perhaps already
too often repeated in different parts of this Eflay)
cm
and the Economy of Fuel. 9t
on the conftruftion of fire-places, my reader will
be able to form a clear and juft idea of the conftruc-
tion of thofe of which I am now fpeaking, (thofe of
the kitchen of the Military Academy, in its frefent
improved Hate) when he is told that the Fire
burns on a circular concave iron grate, about half
the diameter of the circular boiler which belongs to
the fire-place ; that the fire-place, properly fo call
ed, is a cylindrical cavity in the folid brick-work
which fupports the Boiler, equal in diameter to the
circular grate, and from fix to ten inches high,
more or lefs according to the fize of the Boiler ;
that the Boiler is fet down on the top of the cir*
cular wall which forms this fire-place, a fmall open
ing, from three to four or five inches in length
taken horizontally, and about two or three inches
high, being left on one fide of this wall at the top
of it, that the flame which burns Up under the
middle of the bottom of the Boiler may afterwards
pafs round (in a fpiral canal conftrufted for that
purpofe) under that part of the bottom of the
Boiler which lies without the top of the wall of the
fire-place on which the Boiler repofes. The flame
having made one complete turn under the Boiler in
this fpiral canal, it rifes upwards, and going once
round the fides of the Boiler , goes off by an hori
zontal canal, furniflied with a damper, into the
chimney.
In order that the top of the circular wall of the
fire-place on which the boiler is fcated, may not
cover
g 2 Of the Management of Fire,
cover too much of the bottom of the Boiler, its
thicknefs is fuddenly reduced in that part (that is
to fay, juft where it touches the Boiler) to about
half an inch.
The opening by which the Fuel is introduced
into the fire-place, is A conical hole in a piece of
fire-ftone, which hole is clofed by a fit ftopper made
of the lame kind of ftone. The afh-pit door and
its regifter are finimed with fo much nicety, that
when they are quite clofed the Fire almoft inftan-
taneoufly goes out*
The dimenfions of the Boiler, in which the Ex-