A PAPER
ON
CYLINDER CONDENSATION,
STEAM  JACKETS, COMPOUND  ENGINES,
AND
SUPERHEATED STEAM.
BY
GEORGE BASIL DIXWELL.
Read before the Society of Arts at the iMassachusetts Institute of Technology,
Boston, April 29 and AMay 13, 1875.
BOSTON:
FRANKLIN PRESS: RAND, AVERY, & CO.,
117 FRANKLIN STREET.
1875.








A PAPER
ON
CYLINDER CONDENSATION,
STEAM JACKETS, COMPOUND ENGINES,
AND
SUPERHEATED STEAM.
BY
GEORGE  BASIL  DIX'WELL.
Read before the Society  of Arts at the Massachusetts Institute of Technology
Boston, April 29 and May 13, 1875.
BOSTON:
FRANKLIN PRESS: RAND, AVERY, & CO.,
117 FRANKLIN STREET.
1875.








CONTENTS.
"PAGE.
CYLINDER CONDENSATION....  8
ONE REMEDY FOR CYLINDER CONDENSATION......  9
CYLINDER PYROMETER...........10
EXPERIMENTS WITH STEAMER MICHIGAN.......12
USE OF STEAM EXPANSIVELY.........14
PRIMARY CAUSES OF CYLINDER CONDENSATION..... 16
CUMULATIVE ACTION OF INTERNAL METALLIC SURFACES... 20
EXAMINATION OF OBJECTIONS......22
EFFECT OF STEAM JACKETS.........24
EFFECT OF COMPOUNDING........27
AMOUNT OF HEAT CONVERTED INTO WORK IN THE CYLINDER..30
VARIOUS AMOUNTS OF HEAT ABSORBED FROM SUPERHEATED STEAM BY
INTERNAL METALLIC SURFACES........33
ADVANTAGES OF SUPERHEATED STEAM.......33
TEMPERATURE FOUND SAFE IN THE CYLINDER..... 36
SUPERHEATED STEAM A GOOD ABSORBER AND RADIATOR... 37
METALLIC SURFACES WITH SUPERHEATED STEAM IN CONTACT GOOD
ABSORBERS AND RADIATORS........39
THICKNESS OF METALLIC FILM HEATED AND COOLED. 39
SUPERHEATING PROPER FOR EACH CUT-OFF...... 40
ACTION OF CYLINDER PYROMETER.....42
SUPERHEATING IN COMPOUND ENGINES.....45
SECOND METHOD OF SUPPRESSING CYLINDER CONDENSATION... 45
REVIEW........46
TABLE OF MICHIGAN EXPERIMENTS.....5
TABLES OF GEORGEANNA EXPERIMENTS....52, 53








THE following paper, read before the Society of Arts at the
Massachusetts Institute of Technology, Boston, on the evenings
of April 29 and May 13, 1875, has been printed for private
distribution among persons interested in the use and management of steam. If any errors have crept in, I shall be greatly
obliged if the observer will point them out to me by letter addressed to
GEORGE BASIL DIXWELL,
Care of C. P. BOWDITCH.     No. 28, STATE STREET, BOSTON, MASS.








Mr. President and gentlemen of the Society of Arts:
I propose to-night to speak upon the subject of Cylinder
Condensation, and the means of suppressing it in steam and
vapor engines.
I must ask your indulgence while I say a word or two in
explanation, I had almost said in apology, for my speaking at
all before an assembly composed so largely of scientific and
practical men.
The explanation- say apology if you please -must be
found in the fact that steam, air, and -vapor engines have occupied my attention for the last forty years, and that the greater
part of the leisure occurring in the intervals of a business
life has been given to reading such public journals as were
devoted to these and analagous subjects. Moreover, during
the last two years, being entirely unoccupied by other matters, I have devoted myself exclusively to the study of the
particular subject in question, and have given it an amount
of attention which could hardly have been given in six or
eight years by any one compelled to attend to the daily
routine of the business of a mechanical engineer. Moreover,
when I had reached some definite conclusions, I consulted
a practical engineer, who is also a scientific man, and did not
venture to consider them right until they had been checked
by him.
And, finally, I have verified these conclusions by a large
number of experiments, made here under the auspices of the
Institute of Technology.
7




8
Having taken so many precautions to avoid error, I trust I
shall not be considered unreasonable in wishing to lay my
ideas before the Society, in the assurance that they will have
at your hands a frank but liberal criticism.
And now, before going farther, I must (at the risk of being
tedious to the engineers present) explain what I mean by
Cylinder Condensation.
CYLINDER CONDENSATION.
Let us suppose that we are to use the steam  with the
piston at a cut off of one-half or fifty per cent. Now, if we
imagine the cylinder to have been heated to the temperature
of the steam, and then steam admitted until the piston reached
the half stroke, the communication with the boiler then closed
and the steam  allowed to expand through the rest of the
stroke, the exhaust opened and the piston returned; then
upon the steam coming in on the next stroke we should expect to find the internal surfaces in the same condition as
they were at first. But experiments and all experience have
shown us, that in the operations which have gone on during
the first stroke, the internal surfaces have become chilled to a
certain extent, and that a considerable portion of the steam
entering is condensed by them and converted into water. If
you will follow the third line of the " Michigan " experiments,
given in Table 1, and see the percentage of water which is
formed, as compared with the steam  which is worked, you
will see that it is thirty-nine per cent, at about half cut off;
and, I suppose, taking the average of engines now running
(not of course looking only to the best compound engines of
the newest construction), that we may assume about one-third
of the fuel expended in converting water into steam to be
lost in this way. Why and how this happens is a question
which we shall look at farther on. It is a matter of considerable perplexity, and one for which I have found no satisfactory
explanation in publications which have been put in print thus
far. Now, if one-third part of the fuel used in steam engines
is wasted in this way, and if, as calculated, seventyfive




9
millions of tons of coal per annum are used in the steam
engines now running, it would seem that the subject is one,
at all events, to which we may with advantage give an hour's
study.
My attention was first drawn to Cylinder Condensation
and the means of suppressing it, by an article in a prominent Mechanical Journal of London, in which it was pointed
out that a non-conducting cylinder would (if such a thing
were possible) be an effectual remedy. This was in 1871.
ONE REMEDY FOR CYLINDER CONDENSATION.
Reflecting upon this, it appeared to me that such portions
of the cylinder and piston as were not liable to attrition could
be easily covered upon their internal surfaces with non-conducting materials, and that, so far, we should have the thing
required; and it appeared that, in cylinders of large diameter
and short stroke, this alone might be an important improvement. As regards the cylindrical surfaces which are subject
to attrition, no such application seemed possible. But as to
these, a consideration of what happens in the cylinder led to
another device. Condensation being understood to be caused
by the mist formed in the cylinder by the conversion of heat
into work, and by the heat abstracted by external and internal
radiation, and by the deposition of a portion of this mist upon
the internal surfaces, and its re-evaporation during expansion
and during the return stroke, it seemed to me that the difficulty could he in a great measure obviated, if the mist could
be prevented from falling upon the surfaces in question.
Now I happened to be aware that water, in perceptible
drops, was repelled by metals at a temperature decidedly below the 400~, which had been found in practice to be admissible in the working of engines, - that is to say, at about 380~ F.
by iron, and about 335~ F., by copper, - and I proposed, therefore, to prevent the deposition of mist upon the internal
surfaces, by heating the cylinder, before commencing work, to
the necessary temperature, and by keeping it thereafter at the
same point.  This I intended to do by means of a jacket of
2




10
hot air or of superheated steam, regulating the heat by the
indications of a pyrometer, placed in the clearance space, or
in a recess formed for it in the metal of the end of the cylinder.
CYLINDER PYROMETER.
The particular form of this pyrometer, which I adopted, was
only reached after many unsuccessful experiments; but an
effectual instrument was finally obtained by attaching to the
internal surface of the cylinder-head a thin slip of copper,
rolled up into the form of a hollow cylinder, pierced with
many holes, in such a way that its surfaces should be at each
stroke exposed to the action of the steam precisely as the
internal metallic surfaces of the cylinder were exposed. The
examination of many experiments led to the conviction, that
the steam and the internal metallic surfaces of the cylinder
differed but slightly in temperature, so that a pyrometer, of
the form indicated, would give a very close approximation to
the temperature of those surfaces.
The experiments made at the Institute have confirmed this
expectation. The pyrometer has indicated the oscillations of
temperature during every stroke, and has shown itself to be all
that we desired.
In what I have just said, however, I have rather run before
my story.
The article which drew my attention to the subject of cylinder condensation was immediately reviewed by another London
Journal in a leader which ridiculed the ideas put forth by
its contemporary, discouraged all efforts towards the production
of a non-conducting cylinder or its equivalent, represented that
cylinder condensation was after all by no means the formidable difficulty it was supposed to be, and intimated that it was
practically suppressed by means of compound engines and
steam jackets.
Before then proceeding to experiment myself, or consulting
a practical engineer upon the subject, it behooved me to see
whether records of experiments already existing were sufficient to show the precise extent of the evil, and also to show




11
whether it had or had not been thus practically overcome. I
therefore made search for such records of experiments, and
was soon fortunate enough to fall in with those magnificent
quartos, by Chief Engineer Isherwood, in which the matter of
cylinder condensation was so ably and fully investigated.
I examined them with minuteness, recalculated a considerable
portion, and made other calculations, notably those of the
quantity of steam present at the Cut-off (Chief Engineer
Isherwood gave only that present at the end of the stroke),
the times occupied in the strokes up to the cut-off, the thickness of the film of the internal surfaces which was alternately
heated and cooled at each stroke, and various other points
not touched by their author.
And here, before going farther, I must be allowed to express
my admiration for the manner in which the experiments referred to were conducted and recorded, and of the loyalty
with which the results were set down and acknowledged even
when contradictory to convictions previously held and expressed. I look upon these two volumes as an invaluable contribution to mechanical knowledge, and as reflecting the
greatest honor, both upon their author and upon the administration which directed the experiments to be made. I cannot
accept all the theories advanced in these volumes; but the
experiments themselves seem to me worthy of the highest
praise, as furnishing means for the solution of many questions
about which the leading Mechanical Journals appear still to
be quite undecided.
Well, then, I examined these experiments to see if cylinder
condensation was a matter of importance or not. There were
more than a hundred of them made with some fifty different
engines, and I found that, in the experiments with engines
varying from three feet to ninety inches, cylinder condensation showed a pretty uniform percentage for any given cut-off,
and that the experiments with the steamer Michigan, at Erie,
were a fair representation of the average.




12
EXPERIMENTS WITH  STEAMER MICHIGAN.
At the end, in Table 1, is a digest of the experiments in
question. Column one gives the point at which the cut-off
was made in fiactions of the stroke. Column two gives the
point of actual cut-off, including clearance. Column three, the
pressure of steam at cut-off, in pounds on the square inch.
Column four, the weight of water and steam at the cut-off in
pounds: this was ascertained by measuring the water which
was fed into the engine, and the whole amount being divided
by the number of strokes, gives the weight for each stroke.
Column five shows the weight of steam alone, at cut-off, in
pounds, deduced from the pressure given by the indicator.
Column six shows the weight of the water alone at cut-off in
pounds, that is to say, the quantity of steam, which, having
entered as steam, was condensed and formed into spray, which
was partly in the steam and partly deposited upon the internal metallic surfaces. In column seven, we have the percentage which the water at cut-off bore to the steam. I thought it
better to compare it with the steam utilized, because it shows
the actual loss more easily than comparing it with the total
quantity of steam formed.  At a cut-off of 92 per cent,
there is 9 per cent loss; at a cut-off of 72 per cent, 16 per cent
of loss; 39 per cent of loss at the cut-off of 47 per cent; 69
per cent loss at the cut-off of 34 per cent; and the same at a
cut-off of 29 per cent. There is a little irregularity here, but
I suppose experiments never can be expected to be precise.
At the cut-off of 21 per cent, there is 95 per cent loss; nearly
half of the whole steam evaporated was lost, that is to say,
enough steam to have run another engine, if there had not
been any cylinder condensation. Then we have 142 per cent
of loss at the cut-off of 14 per cent, that is, enough steam to
have run another engine and half another. In column eight
we have the weight of the steam at the end of the stroke in
pounds, from which we shall get information hereafter, as to
the action of the steam, and see whether the condensation
occurring after the cut-off is, at any given point, greater or
less than the evaporation occurring after the cut-off.




13
Here I must say a few words in explanation. Let us consider the engine to be running at a cut-off of 47 per cent.
Upon the steam entering, we see 39 per cent of that utilized
is condensed by the action of the metallic surfaces, the
greater part of it probably falling upon the surfaces, a part
of it no doubt remaining suspended in the steam. Now,
upon the moving on of the piston, and a diminution in the
pressure, the water immediately begins to be evaporated;
but as the piston uncovers new surfaces, they, being colder
than the steam, cause a certain quantity of condensation; and
it thus happens that the cylinder, after the cut-off, acts both
as an evaporator and as a condenser, and we gain from  a
comparison of the different experiments a knowledge of
where these two conflicting  actions counterbalance each
other.  We see that at a cut-off of 92 per cent, the steam at
the cut-off weighed 4.450, and at the end of the stroke
4.348: that is to say, there was slightly less steam in the
cylinder at the end of the stroke than at the cut-off.
In the second experiment the same thing. In the third,
2.350 and 2.374, we have a slight increase. In the fourth,
1.696 and 1.671, a slight diminution. There is probably a trifling error in these two experiments, as they do not coincide;
but at 34 per cent cut-off we see that the evaporation from
the ante cut-off surfaces about counterbalances the condensation which takes place as fresh surfaces are uncovered when
the piston moves on.
At 29 per cent cut-off we find that the steam present in
the cylinder at the end of the stroke is greater than the
steam present at the cut-off; that is, the evaporation from the
surfaces before the cut-off is, as the piston moves on, greater
than the condensation upon the surfaces which are uncovered.
And so it goes on until at 14 per cent cut-off we find a very
considerable increase;.686 at the cut-off, and.910 at the end
of the stroke, showing that a very large proportion of steam,
which had been condensed, was evaporated upon the direct
stroke.
A mere inspection of the table of the Michigan experi



14
ments will satisfy any one of the importance of cylinder condensation, and of the fact that the suppression of it is extremely desirable even in medium  and large engines. In
small engines the evil is very much greater, because external
and internal radiation, as also the energy with which the
interior surfaces act, are very much greater in proportion to
the amount of steam  used —this last being as the third
power, while the surfaces are as the square.
THE USE OF STEAM EXPANSIVELY.
The non-professional part of my audience would be likely
to inquire, Why not use the long stroke, at which the condensation is so trifling? and this needs a few words of reply. A
hundred years ago, James Watt, after making his invention of
a separate condenser, drew attention to the advantage to be
obtained from working steam expansively, and took out a
patent for the use of it in that manner. Let us suppose a
cylinder to be worked at full stroke, with an effect, which, for
convenience, we will call six. Now, if we stop the piston at
half stroke, the effect obtained will be three, or half of six.
This is the effect up to the cut-off. But if now we close the
communication with the boiler, and allow the steam to work
by its own force of expansion, we shall obtain an additional
effect, which (were there no Cylinder Condensation or other
deductions to be made) would equal seven-tenths of the effect
obtained up to the cut-off, or seven tenths of three, and if we
made two strokes in order to use the same amount of steam
as we had used in the former case (that of working at full
stroke) the effect obtained would be seven-tenths of six additional. In short, the work done with the same amount of
coal would be increased seventy per cent.
Proceeding in the same way with the case of cutting off at
one-third stroke, the gain is a hundred and ten per cent.
At one-fourth stroke it is a hundred and forty per cent; at
one-fifth it is a hundred and sixty per cent, and at one-sixth
a hundred and eighty per cent. And if we expand sevenfold, the theoretical gain is two hundred per cent, and the




15
total work done is three times as great as would have been
done by the same steam worked at full stroke. Now, during
these hundred years since Watt showed the advantage in
question, engineers have been striving to realize the advantage, but have been greatly disappointed and baffled in their
efforts. The reason of the failure was not, I believe, suspected until a comparatively recent period, when it was suggested that cylinder condensation was probably the principal
cause. But I think this was not demonstrated fully, till
Chief Engineer Isherwood made his experiments.  Let us
look at these as shown in the case of the " Michigan." If
you look at the third experiment, cutting off at forty-seven
and five-tenths per cent, you will observe that the loss by
condensation is nearly forty per cent of the steam utilized.
So you see there disappears from this cause more than onehalf of the gain expected from expansion. Clearance would
take off six per cent more, and back pressure and friction
five pounds per square inch, so that, after making the whole
of these deductions, comparatively little is gained by expansion. And the case is still stronger at the shorter cut-offs, so
that, after proceeding a very moderate distance on the road
of expansion, there is absolute loss instead of gain.
This will be the case even when cylinder condensation is
suppressed; that is, we shall finally reach a point beyond
which, from other causes, expansion will be useless or prejudicial; but we shall be able to carry the expansion a great deal
farther to advantage than it can be carried at present.
Having satisfied myself that the experiments, as shown in
the " Michigan," seemed to demonstrate the very great disadvantage of cylinder condensation, and the necessity of suppressing it, the only thing remaining was to endeavor to
explain how this took place, and this I found exceedingly
difficult; but before accepting the experiments without reservation, it became necessary to have some idea of the manner
in which we were to account for such phenomena.




16
PRIMARY CAUSES  OF CYLINDER CONDENSATION.
There have been attempts to account for them in a variety
of ways. They have been attributed to external radiation;
to conversion of heat into work; to internal radiation; and
to condensation from expansion per se.
Now, as to external radiation: The examination of a great
many experiments led me to believe that in well-constructed
and well-protected cylinders this was not likely to represent
more than one or at the utmost two per cent of the steam
utilized in engines over three feet in diameter. Moreover,
the actual amount of this external radiation would be greater
at full or nearly full stroke than at a short cut-off, because the
cylinder would be hotter, and the direct effect of this cause
upon the surfaces which act upon the steam up to the cut-off
must be still again less in the proportion of their surface to
the whole surface of the cylinder.
As to the conversion of heat into work after the cut-off: The
last column in the table gives us the percentage of the steam
utilized which would be condensed to counterbalance this
cause, and, in comparing it with column seven, we see that
but a very small proportion of the actual condensation in the
cylinder can be attributed to it. The extreme amount at a
cut-off of fourteen per cent is only 12.5 per cent, while the
actual condensation is about 142 per cent of the steam
utilized.
With regard to the internal radiation: Chief Engineer
Isherwood says upon this subject, " If the change in the cylinder from steam to back-pressure vapor could be made without
the deposition and re-evaporation of dew, the temperature of
the interior metallic surfaces would be but very little affected,
because vapors, like permanent gases, receive heat with difficulty either by contact or by radiation, and because of the small
specific gravity of the back-pressure vapor." This was published in his first volume in 1863, when the results obtained
by Professor Tyndall with respect to the absorbing and radiating power of steam were not generally known. These have




17
shown that steam  is not like the permanent gases in this
respect, but, on the contrary, an exceedingly energetic
absorber and radiator of heat. Nevertheless we may form
some idea of the limits to the effects which can be attributed
to internal radiation by the following considerations:
It is evident that the maximum effect possible would be
attained if the whole of the steam in the cylinder were heated
from the temperature corresponding to the back-pressure to
the temperature of the incoming steam. If we take the last
of the " Michigan " experiments, the pressure of the steam at
cut-off was 33 pounds, equivalent to a temperature of 256
degrees.  The back-pressure was 3.7 pounds, equivalent to
a temperature of 150 degrees. Upon our supposition, then,
the utmost that the steam could be heated would be 106
degrees. This multiplied by.475, the specific heat of steam,
would give 50.35 degrees. Dividing this again by the latent
heat of the back-pressure vapor, say 1,009, we have about 5
per cent as the maximum  amount which it is possible to
attribute to the heating of the back-pressure vapor, and if we
consider how instantaneously the greater part of the steam
rushes out upon the opening of the exhaust, I think we shall
conclude that all which can be attributed to this cause will be
nearer two than five per cent.
There is, however, another effect which may be considered
as coming under the head of internal radiation; namely, the
re-evaporation of the spray formed throughout the steam by
the conversion of heat into work. But it is evident that the
maximum which can be attributed to this cause will be found,
if we suppose the whole of this mist to be re-evaporated;
and the result in percentages of the steam utilized will be
found in column ten of the table; and we see that the greatest
percentage, namely, that formed at a cut-off of fourteen per
cent (the last experiment), amounted only to twelve and fivetenths per cent of the steam utilized. But, if we consider
that the radiation from the interior metallic surfaces into a
mass of steam and mist differs materially from the radiation
into a mass of unmingled steam, inasmuch as each layer of
3




18
suspended spray must be an obstacle to the passage of heat
until it has itself been removed by evaporation, and if we
consider that this evaporation (unlike radiation) occupies a
very appreciable portion of time, I think we shall conclude
that it is an extravagant supposition to suppose that the
whole or nearly the whole of the spray produced by the conversion of heat into work can be re-evaporated. At all events,
its maximum at a cut-off of fourteen per cent, or say a sevenfold expansion, has been seen to be twelve and one-half per
cent, and this has already been counted under the head of
conversion of heat into work.
Yet another cause of refrigeration within the cylinder has
been pointed out to me by a young engineer.  This is the
work done in expelling the steam from the cylinder after the
exhaust opens on the return stroke. I mean the expulsion of
that portion of the steam  which rushes out immediately
between the opening of the exhaust and the reduction of the
pressure of the steam in the cylinder to the back pressure
shown by the indicator. But this cause must be minute as
compared with the total condensation shown in column seven,
more particularly as it takes place only on the return stroke,
so that whatever spray is formed must (the greater part of it at
all events) pass out instantaneously without being evaporated
in the cylinder.
We now come to Chief Engineer Isherwood's condensation
of steam by expansion "per se," as described in his " Experimental Researches in Steam Engineering," vol. i., p. 129, and
upon which he relies throughout both volumes as accounting
for the phenomenon of cylinder condensation. It appears to
me that Mr. Isherwood was led to this theory of the condensation of steam by expansion per se by an error in reasoning
which deduced from the experiments of Regnault the very
opposite of that which they show. I will point out where
and how this mistake appears to have been made, knowing
that if I am myself in error it will be immediately shown.
Referring to the experiments of Regnault, Mr. Isherwood
says, "From  them it is well known that the sensible heat




19
increases with increase of density faster than the latent heat
diminishes, and, consequently, that the total heat of a given
weight of steam is greater with greater densities or pressures.
Conversely, with decrease of density the latent heat diminishes faster than the sensible heat increases."   But the
converse proposition, as derived from  the experiments of
Regnault, does not seem to be that with decrease of density
the latent heat diminishes faster than  the sensible  heat
increases, but that the latent heat increases slower than the
sensible heat diminishes.  An example will show this as in
the following table:
Sensible. Latent. Total Heat.
At 120  pounds  pressure..................  341  873   1,214
At 40 pounds pressure...................   267    926  1,193
Difference.............................   74  5321
This certainly seems to show that the total quantity of heat
necessary to keep steam of the lower pressure in the vaporous
form is less than that required to keep the steam of the higher
pressure in the vaporous form, and that superheating, and not
condensation, must arise from the expansion of steam per se
when no external work is done. The percentage, however,
attributable to this cause, could by no means account either
for a great condensation or superheating, as it will be seen
by the above example that the difference in the total heats
amounted to less than two per cent.
The second proposition which Mr. Isherwood took as the
converse of the first, appears in reality to be the reverse, or
what would have been true if Regnault's experiments had
shown the opposite of what they did show.
Now, adding together the maximum possible effects attributable to all these causes, we find they could only produce a
small fraction of the condensation which actually takes place.
How then are we to account for the phenomena? For a long
time I could not imagine any answer to this question, but at
last the following explanation suggested itself: 




20
CUMULATIVE ACTION OF INTERNAL METALLIC
SURFACES.
Let us imagine that upon the first stroke of the piston the
before-mentioned causes abstract from the internal metallic
surfaces which act up to the cut-off an amount of heat to
compensate which a certain amount of steam, say, for instance,
4 ounces, must be condensed upon the next stroke.  Now
let us suppose that upon this second stroke there is, during
expansion and during exhaust, a certain proportion of this, say,
for instance, 3 ounces, re-evaporated. This will chill the
surfaces to an extent requiring a subsequent condensation of
three ounces.  Moreover, during the second stroke, the same
refrigerating causes which were acting before will again
abstract a quantity of heat equal to the condensation of' 4
ounces of steam  as first mentioned.  It is evident, then,
that the  internal metallic  surfaces will, upon  the  next
stroke, condense 7 ounces, and re-evaporate a portion of the
same, and so on increasingly until the heat taken up by the
water re-evaporated by the internal metallic surfaces, plus the
heat abstracted from these surfaces upon each stroke, is equal
precisely to the amount of heat given up by the incoming
steam  condensed by them.  An equilibrium  will then be
gained, and the engine will thereafter work on regularly. If
these surfaces re-evaporate nc  quarter part of the amount of
steam  condensed by them, this last will be 4 times the
equivalent of the heat abstracted from them at each stroke.
If the internal surfaces re-evaporate nine-tenths of the steam
condensed by them, this last will then be 10 times the equivalent of the heat abstracted from them at each stroke, and so
on.  The action of the metal is cumulative, and in this idea,
which I believe to be entirely new, we find a sufficient explanation of the phenomenon.*
* NOTE. - Since the above was written my attention has been called to a communication in "Engineering," March 31, 1871, signed W. Hartnett, and headed
" Compound Engines." In this Mr. Hartnett points out that if heat be abstracted
at each stroke from the internal surfaces, their action will go on increasing until




21
This cause is sufficient to account for the absolute amount
of cylinder condensation, as demonstrated by experiment.
The greater percentage of this condensation observed at the
shorter cut-offs, may be accounted for, first, by the greater
amount of the refrigeration caused by the conversion of heat
into work, and by radiation; and second, by differences in
the cumulative action of the internal metallic surfaces at the
different points of cut-off.
We have already seen that the coefficient, by which the
cumulative action of the internal surfaces multiplies any refrigerating cause applied to them, is greater or less in
proportion as they evaporate a greater or less proportion of
the amount they condense. Now, at a short cut-off, there is a
gradual diminution of the pressure, and less dew will be left
unevaporated upon the opening of the exhaust, when the
instantaneous change causes a sudden and violent evaporation,
attended probably with the formation of spray, by a process
analagous to priming.  It will be readily seen that this
last effect is much more marked with a small measure of
expansion than with a great, because the difference between
the final pressure on the direct stroke, and the back pressure
of the return stroke, is greater.
Having reached this point, I thought myself justified in
dismissing all doubt as to the great importance of cylinder
condensation; and the next question was as to what had or
could be done to suppress it, by means of compounding engines and using steam jackets.
But before proceeding to this question, I would draw
attention to the wanner in which the experiments confute
several objections which have been made to the conclusions
naturally and properly drawn from them.
the condensation and re-evaporation attain a maximum at each stroke. The date
of this article is previous to the one which first drew my attention to the subject
of cylinder condensation, and shows that the idea of the cumulative action of the
internal surfaces is not new as I supposed.




22
EXAMINATION OF OBJECTIONS.
In conversing with an eminent practical engineer, I was
surprised to hear him question whether there really was any
such thing as cylinder condensation. His theory was, first,
that all boilers leaked about 3 per cent of steam; and,
second, that steam, in passing from the boiler, carried into
the cylinder, suspended as spray, about 30 per cent of its
own weight.
Now if you will cast your eye upon the table you will see
the water actually present in the cylinder at the cut-off is, at
92 per cent cut-off, equal to 9 per cent of all the steam
formed, and not to 30 per cent; that at a cut-off of 72 per
cent the water present is equal to 14 per cent of the steam
formed; that at 29 per cent cut-off the water present is
equal to 41 per cent of the steam; at 21 per cent cut-off to
50 per cent; and at 14 per cent cut-off to 60 per cent.  So
you see the results obtained upon the "Michigan" (and
they are just like those obtained with fifty other engines)
positively contradict and overturn the hypothesis in question.
Again, it has been argued, that although steam is condensed
up to the point of cut-off, yet, that much of it is re-evaporated
upon the direct stroke, and that it thus comes to pass that
more work is done than there would have been had there
been no cylinder condensation. Now, let us see what are
the facts.  You will observe that at the cut-offs of 92.1
per cent, 71.6 per cent, and 33.8 per cent, there was less
steam in the cylinder at the end of the stroke than at the cutoff, - that is to say, there was actually less work done up to
a three-fold expansion than there would have been done had
there been no cylinder condensation. If we apply the information thus obtained to the last experiment (that showing a
cut-off of 13.9 per cent), we see clearly that up to 41.1 per
cent of the stroke, or a three-fold expansion, at all events,
there would be loss and not gain, from the balance of the
condensation and re-evaporation between 13.9 per cent and
41.1 per cent of the stroke. In reality, the point at which




23
the condensation and re-evaporation, after the cut-off, balance
each other, must be later than 41.1 per cent of the stroke
in this case, because the refrigerating influences in action
at a cut-off of 13.9 per cent are much greater than those in
action at a cut-off of 33.8 per cent. But even taking it on
the supposition that condensation and re-evaporation balance
each other at 41.1 per cent, in the case where the cut-off was
at 13.9 per cent, we see that the pressure at the end of the
stroke would be increased 34.7 per cent of 5.8 pounds, or
1.52 pounds, and at 41.1 per cent of the stroke it would be
neither increased nor diminished. The pressure then could only
have been increased about -12.  pounds through 58.8 per cent,
or say.448 of a pound through the whole stroke. The average
pressure throughout the stroke was 8.8 pounds, so that the reevaporation (even had there been no loss between the point of cutoff and the point of 41.1 per cent of the stroke) could only have
added 5.1 per cent to the actual work done in the cylinder.
The diagram  below shows graphically the case we have
been considering, and, I think, disposes of the supposition
that much more work is done in the cylinder when there is
condensation and re-evaporation. It is evident that the loss
shown at the cut-off is nearly a total loss, and that the actual
loss on the whole stroke is in the same proportion. This is a
very important point. The mind naturally jumps at the conclusion, that all the steam accounted for by the indicator has
done full and honest work in the cylinder; but yet we see that
in the example just cited, 35 per cent of the steam presentat the
end of the stroke had done really but 5 per cent of the work.
re




24
A similar error was made by a reviewer of one of Mr. Emery's communications regarding cylinder condensation. Mr.
Emery stated, that he had tried a glass cylinder against a metallic cylinder of the same size, and saved half the steam.
The reviewer replied, " Yes, and no doubt the metal cylinder
did twice the work!"  I presume he meant that the reevaporated steam did full work in the cylinder, whereas we
see that it does very little. It is these loose and hasty conclusions that postpone for years the acceptance of valuable
experiments, and retard the progress of mechanical science.
EFFECT OF STEAM JACKETS.
Now as to the extent to which cylinder condensation can be
reduced by jackets. Among Chief Engineer Isherwood's
experiments we have that of the Brooklyn pumping engine, of
ninety inches diameter, and ten feet stroke, covered on its ends
very thoroughly with non-conducting substances, and jacketed
on the sides, which constituted three-fourths of the whole surface. The engine was run forty-two hours with steam admitted to the jacket, and forty-three hours without. Unjacketed, the condensation was 24 per cent of the steam utilized;
jacketed, the condensation was 18.5 per cent of the steam
utilized, besides 2 per cent condensed in the jacket, making a
reduction of 5.5 per cent, purchased at a cost of 2 per cent,
and thus showing an actual saving of three and one-half per
cent only.  The steam in the jacket had a temperature of
244~, the average temperature in the cylinder during a
double stroke being 174~.
There is one other experiment to be found in the volumes
referred to which it may be well to glance at, although it was
with a very small engine (five and one-fourth inches diameter
by ten inches stroke), in which the internal radiation and the
great comparative extent of surface masked the effects of the
conversion of heat into power. In this the steam jacketing
was very thorough, the whole engine being jacketed and the
temperature of the steam in the jacket about 3000, while




25
the mean temperature of the steam in the cylinder during
a double stroke of the piston was about 180~.
In this engine (which by the way was a condensing one),
the steam utilized, that is to say, the aggregate steam present
at the point of cut-off (when this was nineteen per cent apparent, and twenty-five and three-tenths per cent actual), was in
four experiments 1052; while the amount condensed was 741;
besides the condensation in the jacket of 756; making 1497
wasted by condensation to obtain the work of 1052, - the total
steam formed in order to get the work of 1052 being 2549.
It is true that the jacket effected a great deal in this engine,
inasmuch as the steam utilized without it was only about one
fourth of the whole amount formed; but the example is instructive, as showing that the jacket (even when the metallic
surfaces are enormous as compared with the quantity of steam
used) cannot suppress cylinder condensation. The action of
this engine appears to justify the opinion that there is no advantage in adding a condenser to small machines, for reasons
shown farther on.
Before quitting the subject of the efficiency or inefficiency
of jackets, it may be well to look a moment at the recent
experiments made at the Charlestown Navy Yard upon the
" Rush," "Dexter," and " Dallas."
The "Rush " was a compound engine, thoroughly jacketed;
and we can compare its performance in the low pressure
cylinder, as to utilization of the steam evaporated, with that
of the other two vessels which were not jacketed. In the' Rush," we are told that the indicators accounted in the high
pressure cylinder for 93 per cent of the whole steam formed,
and that they accounted for 73 per cent in the low pressure
cylinder. Now, undoubtedly, a portion of the 7 per cent lost
in the small cylinder went over as spray into the large cylinder; but it is highly probable that about 97 per cent of all
the steam found its way as steam into the latter. In this case
the loss in the low pressure cylinder would be 27 per cent
less 3 per cent, supposed to have been absolutely lost in the
first cylinder, or say 24 per cent of all the steam formed.




26
Now the proportion of the steam, which the indicators
accounted for upon the long run of the "Dexter," was 68
per cent, showing a loss of 32 per cent; but then the "Dexter " was working at an actual cut-off of about 32 per cent,
while the actual cut-off in the large cylinder of the " Rush"
was nearly 52 per cent; and the condensation ought, therefore, to have been very much more in the " Dexter " than that
of the " Rush."
Again, in the long run of the " Dallas " (cutting off actually
at about 32 per cent), the proportion of water accounted for
by the indicators was 74 per cent, showing a loss of 26 per
cent, a performance very much better than that of the large
cylinder of the " Rush," if we make allowance for the great
difference in the ratios of expansion. From these experiments, one would almost conclude that the jacket on the low
pressure cylinder was worse than useless; but I would not
uphold this proposition. I think, however, that the experiments go to show that the steam jacket does but very little
towards suppressing cylinder condensation in the large cylinder of compound engines or in the single cylinder of other
engines. It is very difficult to form an opinion as to the effect
produced by the jacket upon the smaller cylinder. The indicator shows but little condensation, but this may have arisen
from superheating, about which the record of the experiments gives no information, and also from the high back
pressure and consequent smallness of the difference of temperatures in the small cylinder. It would seem a priori to be
very improbable that the jacket should have a great effect
upon the high pressure cylinder, because the difference of
heat between the boiler and jacket steam and the average
of the steam in the cylinder is comparatively small.
Before entirely leaving the subject of the efficiency of
steam jackets, I must say a word with respect to the experiments made upon the compound engine of the " Bache."
In experiment one, without jacket, the indicator of the small
cylinder accounted for 65 per cent of the steam  which
entered, and the indicator of the large cylinder accounted for




27
53 per cent, giving an average of 59 per cent; while in experiment four, with jacket, and at about the same rate of
expansion, the indicator of the small cylinder accounted for
58 per cent of the steam entering, and the indicator of the
large cylinder for 74 per cent, giving an average of 66 per
cent. This showed a gain of about 12 per cent, but there
still remained a loss by condensation of 34 per cent of all the
steam formed, or about one-half of the steam utilized. Had
this been saved, by suppressing condensation, the indicated
horsepower in experiment four would have cost 17 pounds
of water instead of 25, and 1.8 pounds of coal instead of 2.7
pounds.
It must be observed that the " Bache " had a small engine,
the effect of the jacket upon which must have been much
greater than could be realized with engines of greater size.
This is all I have time to say upon the subject of steam
jackets.
EFFECT OF COMPOUNDING.
When we turn to the effect of compounding engines, we find
a great advantage. The " Rush \ expanding altogether 6.2
times, lost 7 per cent in the high, and 27 per cent in the low
pressure cylinder, giving an average of only 17 per cent;
that is to say, 100 pounds of steam did the work of 83 pounds,
whereas in the "Michigan " a hundred pounds of steam, at
about that rate of expansion, would only have done the work
of 50 pounds. It is not difficult to see how this happens.
The condensation in the " Michigan " experiments, at a cutoff of 47 per cent, was 28 per cent of the steam formed, or
very nearly what occurs in the large cylinder of the " Rush,"
while with a cut-off of one-sixth, condensation in the "Michigan" experiments was fully 50 per cent. Now this fifty per
cent counted against the whole work done by the " Michigan,"
but the 27 per cent, lost in the large cylinder of the " Rush,"
counted only against about one-half the work done by the
"Rush," and so represented only 13.5 per cent as compared to
the whole work. The steam  in the small cylinder of the
" Rush" lost only 7 per cent, or about 3.5 per cent compared
with the whole work done by the engine.




28
There would be a real advantage in dividing the expansion
between two cylinders, even if the condensation were equal
in each, because the steam condensed in the first cylinder,
being almost wholly re-evaporated, does full work in the
second cylinder, that is to say, the full work that could be done
by fresh steam from the boiler; but the gain may, perhaps,
be much greater on account of an important reduction in the
condensation of the steam of the small cylinder, growing out
of the fact that it exhausts against a considerable pressure, so
that a smaller proportion of the steam condensed up to the
point of cut-off, is re-evaporated during the expansion and
during the exhaust.
I have not been able to verify this, but I think that we may
see reason to expect a small condensation in the high pressure
cylinder of a compound engine as compared with that in a
low pressure cylinder of the same size; for evaporation, it is
well known, is in inverse proportion to the pressures, other
things being equal; so that of the steam condensed up to the
cut-off, less will be evaporated, if the back pressure be high
than if it be low; and as in the high pressure cylinder the
back pressure is several times that in a low pressure cylinder,
the condensation should be much less than in a low pressure
cylinder of the same size. If (to revert to our original example) four ounces of water be formed in a cylinder at each
stroke, and only one-half of it be re-evaporated, then the
heating and cooling will become equal, and the engine work
on steadily as soon as the condensation is twice that due to
each stroke. The cumulative effect of the metallic surfaces
will then stop; whereas, if three-quarters of the water and
spray formed at each stroke be re-evaporated, the cumulative
action will cease only when the condensation is four times
that due to each stroke. If seven-eighths be re-evaporated, the
cumulative action will not stop until the spray formed equals
eight times that due to each stroke. I think this also accounts
for the empirical fact, or at all events, the belief, before unexplained, of the uselessness of condensers in very small engines.
In these engines, working with condensers, the energy of the




29
internal surfaces is enormous, entirely masking the effect of
the heat converted into power. I have already quoted one
of Chief Engineer Isherwood's experiments on a cylinder,
five inches diameter, ten inches stroke, in which 4 pounds
of steam were evaporated, to do the work of one, when the
cut-off was 25 per cent, whereas, in the engine belonging to
the Mechanical Laboratory of the Institute of Technology,
of eight inches diameter and two feet stroke, working without
a jacket and without a condenser and at 25 per cent cut-off,
1.6 pounds of steam evaporated, did the work of one; or, in
other words, the percentage of cylinder condensation in the
engine with a condenser was five times that obtained in the
other without a condenser.  No doubt the engine of the In.
stitute being more than double the size of the other, would
give better results, even if worked with a condenser, but
the size was not sufficiently greater to account for the immense difference of performance observed.
The varying proportions of the condensation observed at
the different cut-offs seem to be due chiefly to the varying
amounts of power developed during expansion. The formidable amount of the condensation is due to the cumulative
action of the metallic internal surfaces. I am speaking now
of medium  and large cylinders.  In very small cylinders,
radiation, external and internal, and the immensely greater
surface, cause in themselves an enormous condensation.
I have now described to you the steps by which I reached
the conclusion that cylinder condensation was a very formidable evil in steam engines; that it was but very little reduced
by steam jackets, and that even in the best compound engines
it still caused a loss of some 17 per cent of the whole steam
evaporated, or over 20 per cent of the steam utilized. I hope
to show hereafter how the performance of even these may be
increased some 35 per cent by an expenditure of 10 per cent
of heat.
Having reached these conclusions, I thoughhit time to take
professional advice; and I applied to a practical engineer,
who is also a scientific man, a member of this society, and a
professor in one of our scientific institutions.




30
I laid my calculations before him, and we had many and
long conferences upon the subject; and finally came to the
conclusion, that the means I proposed to apply would probably
be effectual, and that at all events they were worth a trial
experimentally.
AMOUNT OF HEAT CONVERTED INTO WORK IN
THE CYLINDER.
But during one of these conferences, we brought under
discussion the question of whether it was right to calculate
the refrigeration produced in the cylinder from the heat converted into work by taking the whole work done in the
cylinder, as was done by Chief Engineer Isherwood, or by
taking only the work done after the cut-off. We agreed that
it was reasonable to take the work done after the cut-off,
inasmuch as the previous work was done by the whole steam
in the boilers, but that it was desirable to have this settled
by experiment; and it then occurred to me that an answer to
the question might, perhaps, be obtained from Mr. Isherwood's
experiments with superheated steam, made on board the
steamship "Georgeanna," in Chesapeake Bay;  for if Mr.
Isherwood's hypothesis were correct, the temperature of the
superheated steam in the cylinder, counting from a given heat
in the steam chimney would be less than on the other hypothesis; or, what is the same thing, the temperature in the
steam chimney, deduced from the ascertained heat in the
cylinder, would be greater upon Mr. Isherwood's hypothesis
than upon the other.  If the correct temperature of the
steam before entering the cylinder had been obtained, the
problem would have been of easy solution; but, unfortunately,
the correct temperatures were not obtained. The thermometers immersed in the steam chimney and in the superheater
showed less than the truth: how much is not known. Chief
Engineer Isherwood thought it (the temperature of the
steam before entering the cylinder) was about 4000; but it
was certainly much more than that, inasmuch as fully 500~
was apparent in the cylinder in two of the experiments.




31
That is to say, the normal temperature due to the indicated
pressure added to the heat necessary to produce the increase
of volume observed, proved that the actual temperature was
500~; even at the end of the stroke it was 433", and as the
steam must have supplied the heat abstracted by radiation,
say 50~, the actual temperature in the superheater could
hardly have been less than 483~, even without supposing it to
balance the heat abstracted by the work done in the cylinder.
But this heat (the equivalent of the work done) must have
been taken from  the steam, and the only question was,
whether the steam in the cylinder had to supply the equivalent of the whole work done, or only the equivalent of the
work done after the cut-off.  It was on precisely this point I
was cross-questioning the experiments in question. Calculating the equivalent of the whole work done in experiment D,
it proved to be 2890; and deducting 16" for the excess of heat
contained in higher pressure steam at the cut-off over that at
the end of the stroke, we still have 2730, which, upon Mr.
Isherwood's hypothesis, must have been in the steam before it
entered the cylinder over and above the before mentioned 4830.
We arrive then at the astounding figure of 756" as the temperature of the steam in the superheater. The highest temperature shown by the thermometers placed in the steam actually
used was 338", which Chief Engineer Isherwood observed
was probably 750 too low, and the highest temperature shown
even in the superheater was 5440, which was thought to be
60~ too low. I ought to have explained that the " Georgeanna,"
about which I am now speaking, had a large heating surface
in the steam chimney which was sufficient to produce a considerable superheating, and that she had also a separate and
very large superheater. The steam  from the chimney and
the superheater was led into the cylinder in such a manner
that the quantity of that from one or the other source could
be increased or diminished, and in this manner it was proposed to regulate the amount of superheating.  Now there
were seven experiments which gave a total heat necessarily
existing in the steam before entering the cylinder of 538~,




32
609~, 684~, 756~, 592~, 678~, 761~, shown on line ten of the
table on page 52, proceeding upon the hypothesis before
mentioned. But calculating only the equivalent of the work
done after the cut-off, I found a much lower series.of temperatures; namely (those found on line ten), say 3970, 444~, 521~,
555~, 452~, 505~, 5660.  But even these you will observe to
be very high, as compared to the numbers on line twelve,
which are those considered  probable  by Chief Engineer
Isherwood.
In fact, the hypothesis of Chief Engineer Isherwood leads
us to temperatures which could not have existed in either
steam  chimney, or superheater; and even upon the other
supposition, namely, that the' steam in the cylinder supplied
only the equivalent of the work done after the cut-off we
still obtained temperatures which show the thermometers to
have been a great deal wider of the mark than would have
been thought possible; but that they were thus erroneous,
may be shown indirectly as follows: Experiment B was made
using the steam chimney without the superheater, and that
alone was sufficient to suppress all condensation so that the
temperature of the steam before entering the cylinder must
have been upon our hypothesis 444" at a cut-off of 66 per
cent; and that this is not too high, is evidenced by the fact
that in the " Eutaw" experiments, at a cut-off of 58 per cent,
steam of 3940 temperature did not entirely suppress cylinder
condensation. We are justified, then, in taking the temperature in the steam chimney of the " Georgeanna," at say 440~.
This investigation appeared to me, as well as to my practical adviser, to settle experimentally the question we had
under consideration, and to show conclusively that the equivalent of the work done after the cut-off (and not the equivalent value of the whole work) was abstracted from the steam
in the cylinder. And here I cannot but point again to the
importance that experiments should be fully described in
every detail so that subsequent investigators may carefully
examine them, and perhaps deduce from them  answers to
questions not thought of when the experiments were made.




33
VARIOUS AMOUNTS OF HEAT ABSORBED FROM
SUPERHEATED  STEAM  BY INTERNAL METALLIC
SURFACES.
This has, I think, already been made apparent, but it will
become still more so a little farther on; for while I was
making the investigation, just described to you, a very unexpected, extraordinary, and important fact leaped out upon
me; namely, the fact that if we heated our steam, to say
550~ in the superheater, and introduced it into a cylinder
working at about two-thirds cut-off, we should (at the point
of cut off) find a temperature of about 500~; but if we introduced the same steam into the same cylinder, changing only
the point of cut-off to one-half what it was before, and
placing it at the point of one-third instead of two-thirds, then
we shall find in the cylinder a temperature at cut-off of only
274~. How could this happen? Before going fully into this
I must say a few words upon other subjects.
ADVANTAGES OF SUPERHEATED STEAM.
I had, many years ago, and many times, considered the subject of superheated steam, with a view to obtaining in practice the theoretical advantage there is in using it, which
advantage I will endeavor to make manifest to the non-professional portion of my audience, inasmuch as it can be done
in a very few words. The figure represents a cylinder open
at the top, and having a piston at half stroke, or just in the
middle of its length.
If, now, we suppose the area of this piston to be exactly
one square foot, and its height from the bottom to the middle
where the piston stands to be 26.3 feet, we shall have represented in the space, A B C D, included between the piston and
the bottom and sides of the cylinder, the precise space which
is occupied by one pound of steam at the pressure of the
atmosphere. Let us now imagine the piston to be at the
bottom of the cylinder, and that from a boiler we introduce
steam  so as to raise this piston, supposed to be without




34
weight and to move without friction, 26.3 feet. The work
we shall have got out of the steam will be equal
to the pressure of the atmosphere upon one
square foot of surface raised 26.3 feet, or say in
round numbers 2160 pounds raised 26.3 feet; and
the cost to us of doing this work will be measured
by the total heat, or say 1146~, if we suppose
the water to have been at a temperature of 32~
F., or, say 1120~, if we suppose the water to have
been at a temperature of 58~ before entering the
boiler. That is, a quantity of heat sufficient to
A X     B  heat one pound of water 1120~ F., is what we
have to expend in order to raise 2160 pounds
26.3 feet with steam of atmospheric pressure.
But the temperature of this steam is 212~ F., or
counting from the absolute zero it is 673~, and by
the law which has been ascertained to govern the
action of gases and vapors, and which is very
nearly true of both, we know that by doubling
the temperature of the steam in the cylinder we
___     can double its bulk, so that we shall have then
raised our 2160 pounds, or the weight of the atmosphere, not 26.3 feet, but just double that space. That is,
we have done in the last half of the cylinder exactly the same
amount of work we had before done in the first half; but
when we come to count the cost, we find a notable difference; for, in the first place, we expended 1120~ of heat, and
in the latter 673~; and this is not by any means the whole
of the difference, for the 1120~ of heat are degrees measured
by water; that is to say, the 1120~ represents an amount of
heat adequate to raise the temperature of one pound of water
1120~; while the 673~, used during the last half of the stroke,
represents the amount of heat necessary to raise the temperature of one pound of steam 673~; and one pound of steam can
be raised 673~ with much less heat than one pound of water,
the proportion being as 475 to 1,000, so that, to compare our
two expenditures, we must multiply 673 by 475, and divide




35
by 1,000. This gives us 320~, and shows that the 673~,
which, added to one pound of steam, will double the work
done, is equal to 320~ added to one pound of water. But we
found before, that our power obtained from steam, evaporated
from water, cost us 1120~; so that the power obtained by
superheating has cost only -3-2-tohs of what we had to expend
to obtain the same work out of steam formed directly from
water; or, in brief, an amount of fuel used in superheating
will do three and a half times the work that the same fuel
can do in forming ordinary steam  from water. Here is an
enormous advantage. This has been manifest to the scientific
and mechanical world for a great number of years; but the
practical difficulties, in the way of securing this advantage,lie
in the high temperatures requisite. The oils used in lubrication are decomposed (often into acid substances) at about
450~; and metallic surfaces, working upon each other without oil at high temperatures, are destroyed.  What this temperature is, does not appear to be accurately determined.
Chief Engineer Isherwood calls it 400~, but in the experiments with the " Georgeanna," already referred to, it is evident that a temperature of about 500~ existed in the cylinder in *
two of the experiments (those made at a cut-off of 65 per cent)
during two runs, which each continued for seventy hours and
upwards; and Mr. Isherwood (although prejudiced against the
use of superheated steam, which he had in his first volume declared to be destructive to valves, piston, and cylinder,) bore
witness to the facts, that the cylinder of the " Georgeanna"
was found, upon examination, to be like a mirror, and the
valves and valve seats perfect after a constant service of
two years with the superheated steam.
I do not by these remarks mean to depreciate the value of
the experiments of Mr. Isherwood, of which I have already
expressed the highest possible opinion; but to show, on the
contrary, the fidelity with which what was seen and done was
reported, regardless of preconceived opinions.
We see that he reports the engine of the " Georgeanna"
to have been in perfect order, notwithstanding his previous
*   rhis conclusion rests upon the correctness ot the assumed evaporative
efficiency of the Georgeanna's boilers. If the actual evaporation wan
10 per cent greater than the assumed, the above 500~  would be reduced
to about 425~.




36
opinion that superheated  steam  was destructive, and he
shows the " Georgeanna" developing a total indicated horse
power from 16.4 pounds of water and 2.2 pounds of coal per
hour at a cut-off of 28 per cent, while the engines working
with saturated steam required 30.5 pounds per horse power
per hour.
It is to be remarked that this performance of the " Georgeanna" with the usual type of single-cylinder American engine
about equals the performance of the "Rush," built on the
latest form of compound engine, which used 16.1 pounds of
water, and 2.1 pounds of coal per horse power per hour. I
do not say this as against the principle of compounding, for
I believe this principle to be destined (when combined with
judicious superheating) to give even better results; but I
wish to note the fact with regard to the " Georgeanna " as
indicative that the existing engines, with the additions of
superheaters properly watched and regulated, can be made to
do as good work as has ever been performed up to this day.
TEMPERATURE FOUND SAFE IN THE CYLINDER.
To revert to the temperature which may safely be used in
a steam cylinder. This is a very important point, as upon
it depends the amount of gain which we can make by superheating. We see that the " Georgeanna " worked 140 hours
with a temperature of 500 degrees and a cut-off of 66 per
cent, and was uninjured; but I do not know whether she
was usually worked at the cut-off in question. If so, it would
appear to settle the matter, and prove that 500 degrees can
safely be used. But if the usual cut-off was, as is probable,
45 per cent, we have only a heat of about 370 degrees as that
existing in the cylinder during the greater portion of the two
years run.
Let us take 400 degrees as the limit of safety; then, as the
steam at present generally used has a temperature when
saturated of some 300 degrees, we have only 100 degrees left
for superheating, and this only adds about one-seventh to the
effect, and would hardly be worth the additional complication
S:em note page 35.




37
of a superheater. You will perceive that I am arguing upon
the supposition that superheated steam carries into the cylinder its own temperature, and I think it was generally
believed that such was the case, and that steam when superheated took upon it the properties of a permanent gas, those
of atmospheric air for instance, so far as regarded its action
towards and under the operation of heat. Now, atmospheric
air parts with and takes up heat with great slowness, and if
heated to 550 degrees in a boiler, and thence carried into a
cylinder, would beyond question destroy the oils then present
and injure the metallic surfaces. It was supposed that steam
was of the same character, and you may judge then of my
astonishment when (during the investigation with regard to
Joule's equivalent, already detailed,) I observed that steam,
which must have had a temperature of 450 degrees and
upwards in the superheater, was found in the cylinder at the
cut-off to have only the temperature of 274 degrees, as
already stated upon page 33. In a moment it had lost something like 200 degrees of heat.
SUPERHEATED STEAM A GOOD ABSORBER AND
RADIATOR.
Here was an astounding fact; for you will observe that the
condition of things was totally unlike that existing where
saturated steam was used, because in this latter case a portion
of steam, being condensed into water, brought a fresh portion
into contact with the metallic surfaces, and so on; whereas,
in the case of the superheated steam, we had in presence of
each other, the steam, which I then supposed to be, like air, a
very bad absorber and radiator, and the metallic surfaces,
which were notoriously so. How could these bad radiators
and absorbers interchange their heat in so small a space of
time as to be practically instantaneous? It seemed improbable
to the last degree, and any other possible supposition appeared
preferable. Could it not be that the steam lost its superheating in the pipes and passages before reaching the
cylinder? Might it not be that the experiments were in some
respect faulty?




38
Another equally astonishing and unexpected fact answered
these questions in the negative.
In the particular experiment which brought out most distinctly the phenomena under consideration, the steam at the
point of cut-off (28 per cent of the stroke) had lost all its
superheating, and remained at the point of saturation, but
without any condensation. There was in it no superheating
to counterbalance the heat abstracted for the performance of
work after the cut-off, and this equalled 188 degrees (measured by steam, not by water), and even after deducting the 42
degrees of excess of heat existing in the steam at cut-off over
that of the lower steam at the end of the stroke (this also
measured by steam), there were still 146 degrees to be furnished from somewhere; and, adding a moderate amount for
radiation, there were certainly about 200 degrees. Condensation during the stroke would seem therefore inevitable;
but so far was this from being the case that the steam at the
end of the stroke was absolutely superheated some 46
degrees. Where then did these 246 degrees come from?
Certainly not from the steam, for at the point of cut-off this
was precisely, or almost precisely, at the temperature of
saturation - it had no extra heat to part with, except the 42
degrees excess which exists in the steam of the pressure
used at cut-off over that of the pressure found at the end of
the stroke. At least 200 degrees then could only be accounted
for on the supposition that the metallic surfaces gave it out
during expansion.
I examined the experiments in every imaginable way in
the expectation of finding some error, but did not succeed in
finding any, and I remained for some time in a state of bewilderment regarding them, until the experiments of Professor
Tyndall upon radiant heat swept away one of the difficulties
by showing that the vapor of water was not like air, a bad
radiator and absorber, but on the contrary one of the best to
be found in nature.




39
METALLIC SURFACES WITH SUPERHEATED STEAM
IN CONTACT GOOD ABSORBERS AND RADIATORS.
There still, however, remained the perplexing fact that
metallic surfaces, especially polished ones like the walls of
cylinders, were among the worst radiators and absorbers
known; and it was difficult to imagine that they could be
made to receive and deliver the heat, however capable the
steam itself might be to deliver and receive it.
I finally, however, found the explanation in the same experiments of Tyndall, when he showed that a Leslie's cube,
filled with boiling water, produced scarcely any effect upon
the thermo-electric pile when a bright metallic surface was
presented to the pile, whereas, when the same metallic surface
was varnished, heat suddenly gushed out; and, still more, he
showed that a thin film of a powerfully radiating gas, like
olefiant gas, when passed over the surface of the polished
metal, produced an effect analogous to the varnish, - taking
up heat from the metal by contact, and passing it out upon
the pile by radiation.
Now a precisely similar effect evidently takes place in the
cylinder. The metallic surfaces are bad radiators, -among
the worst,-but the thin film of steam immediately adjacent
becomes heated by contact, and then pours out the heat with
the velocity of light into the great mass of steam. All this
occurs in an inappreciably short space of time, and the feeble
radiator, varnished by the steam, becomes converted into a
very energetic one.
THICKNESS OF METALLIC  FILM  HEATED AND
COOLED.
The phenomena observed in the cylinder being thus found
to be in accordance with others which are well ascertained,
may therefore be accepted as no longer improbable. The
facts in the particular experiment referred to were, that the
steam at the end of the stroke had a temperature of 2560, and
we may assume that a thin film of the internal metallic sur



40
faces had also this temperature.  During the exhaust a
further reduction must have taken place; but this further
reduction could hardly have been great, inasmuch as the
greater part of the steam  rushed out in an exceedingly
minute space of time, leaving but very little in the cylinder
to abstract heat from it. It appears to me to be a sufficient
allowance, if we suppose the film in question to have been
reduced to the temperature of say 244~, or 300 less than the
temperature at the cut off.
Now the total weight of steam which passed through the
cylinder during the experiment was 920,000 lbs., and the
number of single strokes was 223,464; so that the steam
present at the cut-off weighed about 4.12 lbs. As the specific
heat of steam is.475 while that of iron is.114, and as 4.12
lbs. lost 2000 of heat upon entering the cylinder, while the
film of iron, which we will call x, gained 300, we have the
equation
4.12 lbs. X 200" X.475- x X 30" X.114
from which x = 114.4 lbs. But the metallic surfaces, present
at the point of cut-off, measured 56.59 square feet. This
surface, an inch thick, weighs 2124 lbs. Then 2124:114.4
1 inch: 15-4ths of an inch. We thus find that less than
-th of an inch in thickness was sufficient to absorb and give
out the heat equivalent to the power developed after the
cut-off and the radiation.
SUPERHEATING PROPER FOR EACH CUT OFF.
And these phenomena led to a very important conclusion,
namely, that steam might safely be superheated sufficiently to
balance the radiation, and the heat converted into work without any fear of its carrying into the cylinder a temperature
injurious to the working parts, inasmuch as if only superheated to that extent, the temperature  apparent in the
cylinder would only be the normal temperature of saturation.
And it led also to the further conclusion, that the superheating
might be safely increased beyond the point named, by the




41
number of degrees existing between the point of saturation
and the temperature of 400~, which we. suppose to be safe, or
to such other temperature as experiment should hereafter
prove to be safe.
For instance, taking experiment E on board the " Georgeanna," we find the normal temperature of the steam at cut-off
tohave been 274~, the heat converted into work 188~, and the
greater heat, contained in the steam at the cut-off over the
steam at the end of the stroke, to have been 42~. Deducting
420 from 1880 we have 146~, which, added to 2740, gives 4200
as the point to which at this cut-off the steam might be superheated, if our object was simply to suppress cylinder condensation. To balance radiation, a further amount of superheating would be necessary, and if we take this to be 500 we
should have 4700 as the point to which we should go in the
superheater; and this would give only the heat of saturation
at cut-off in the cylinder, or say 2740.  But as 4000 is
known to be safe, we might still increase the heat in the
superheater by 4000 - 270~, or say 126~, and make the heat
in the superheater 470~ + 126 -= 5960, so that at this cut-off
5960 in the superheater would bring about only a temperature
of 4000 in the cylinder, giving us a total suppression of.cylinder con'densation, and also an increase of power 4 —+46-=  5- or about ith of that actually developed in the experiment in question, in which the total horse power cost 16.4
pounds of water evaporated. If the superheating had been
carried to 5960 to obtain 1 greater power, we should have
had l1th horse power for 16.4 lbs. of water, or 6 =-X14 -- 9   -=
14.1 pounds of water nearly for a horse power. Of course
we should have had the expense of superheating, but this
would have been only 596~ - 274~ =3220 measured by steam
or 3220 X.475, the specific heat of steam, or say 153~ measured
by water. The cost of evaporating the steam being 1120~,
the above 153~, representing the expense of superheating,
would have been about 14 per cent. That is, at an expense
of 14 per cent, we should have entirely suppressed cylinder
condensation, or a loss of about 69 per cent, and have gained
ith in power besides, or about 16 per cent.




42
But the experiments showed another fact: namely, that what
was safe at a cut-off of 28 per cent, and necessary in order to
get the best results, would be unsafe at 66 per cent cut-off,
and we should then have to reduce our superheating some
74~, and so on for each different cut-off; and in this fact we
find, I think, why thus far so little success has been had with
superheated steam. If not sufficiently superheated, cylinder
condensation is not suppressed; while if the superheating be
carried too far, the engine is injured, and this last might easily
happen under an engineer not informed of the facts I have
just been bringing before you. He might have been working safely for a year at a cut-off of one quarter, and then,
upon some exigency arising for the use of a longer cut-off,
he might destroy or greatly injure the cylinder and valves if
he changed the cut-off without correspondingly changing the
amount of superheating.
But no rule can be given beforehand for the change in
superheating to be made for a given change of cut-off. This
must either be ascertained by experiment upon the particular
engine used, or, what is much more convenient, the heat of
the steam in the cylinder should be ascertained continually
by a pyrometer placed in the clearance space, or in a cavity
cut for it in the metal of the cylinder cover. An instrument
of this kind is described in one of the patents recently granted
me at Washington, and one is to be seen here, attached to the
engine of the Mechanical Laboratory of the Institute of
Technology.
ACTION  OF CYLINDER PYROMETER.
It may be interesting to my audience to know how the record
of this instrument verifies the truth of the foregoing statements and confirms the theory that the internal metallic surfaces act in the way suggested.
The action of this pyrometer, as influenced by the heat of
the steam in the cylinder, is shown on the front of the
engine, where a short pointer before the face of a graduated
dial is free to move backward or forward when any change




43
in temperature occurs, thus manifesting to the eye of the
observer the relative thermal condition of the steam while it
is doing its work in the cylinder. To show how effective it is
in recording a difference in temperature, it is sufficient to
state, that when the engine is worked with ordinary saturated
steam, used expansively, the pointer makes large oscillations
during each revolution of the engine, jumping forward instantly, whe.n the opening of the admission valve allows steam
to pass into the cylinder, and falling slowly backward during
the expansion and exhaust. The. amplitude of this motion,
when the steam is cut off at one-eighth stroke, reaches more
than one-half a complete turn of the pointer on its pivot, and
continues thus as long as the engine runs. Its sudden jump
to its maximum indication, when the hot steam enters the
cylinder, is made simultaneously with the first impulse given
to the indicator pencil when the steam rushes in with its high
initial pressure; and the two instruments show almost exactly
the same relative changes going on in the cylinder during a
stroke, although the one indicates the temperature, while the
other indicates the pressure of the steam. This pyrometer
thus tells the story that the greater heat present in the steam
at the cut-off does not superheat the expanding steam of
lower pressure, but simply diminishes the condensation due to
the work done and to radiation, leaving still a great variation
in temperature.
From its indications, however, when the engine is working
with superheated steam, we may infer an entirely different
state of things. In several experiments which have been
made with the use of superheated instead of saturated steam
with different measures of expansion, the oscillations of the
recording pointer were of very much less extent. The arc
passed over by the pointer in these vibrations did not exceed
7~ in any experiment, which is hardly perceptible when compared with the oscillation of 200~, just referred to in a similar
experiment with saturated steam.
This shows conclusively that there was very little change
in the temperature of the superheated steam in the cylinder,




44
notwithstanding the variation in the pressure which occurred
in the same way as when saturated steam was used.
There seems no other explanation than that already advanced, that the hot steam on entering the cylinder instantly
gave up heat to the internal metallic surfaces, which, as the
piston moved on, radiated into the steam a sufficient quantity
of heat to keep its temperature nearly uniform notwithstanding radiation and work done. The evidence of this instrument corrobates the theory, and shows to the senses that the
internal metallic surfaces act as an absorber and radiator, and
serve as an agent to retain the heat of the steam till it is
needed to prevent condensation.
The results of experiments with this instrument also clearly
show  the necessity of regulating the temperature of the
steam in the superheater to correspond with the particular
cut-off in use. An example will illustrate this point. The
engine was working at a cut-off of three-fourths, a boiler pressur6 of seventy pounds on the square inch, and a temperature
of 410~ in the steam pipe. Without changing any condition
in  the  experiment, save  shortening the cut-off to onehalf, and varying the load to correspond, the pointer of the
cylinder pyrometer, which had previously been oscillating
through an arc of 6~ and showing quite constant indications,
immediately fell 500 and began to oscillate through an arc of
28~; that is, the vibrations which had previously taken place
quite uniformly between the points, ninety-four and one hundred, immediately after the change in the cut-off, dropped 50~
and began to occur between the points twenty and forty-eight.
It was necessary to raise the temperature of the steam in the
steam pipe 40~ or to 4500 in order to bring up the indications
of the pyrometer to their original figure; and when this was
done the previous uniformity was afterward  maintained.
Again, when the cut-off was changed in a similar manner to
one-fourth, there was another fall of 50~ in the indications, and
a similarly large amplitude of the oscillations, which continued until the temperature of the superheated steam, supplying the engine, was still farther increased 100~, bringing it up
to 550~.




45
This demonstrated fully that the temperature of the steam
in the cylinder remains constant even when the temperature
in the steam pipe is increased, provided that a proper shortening of the cut-off is at the same time effected, In the experiments referred to, the superheating was carried to 410~ when
the engine worked at three-fourths cut-off, to 4500 when
working at one-half cut-off, and to 550~ at one-fourth cut-off.
SUPERHEATING  IN COMPOUND  ENGINES.
It will be seen at once, that superheated steam is particularly applicable to compound engines, as these present us with
the opportunities for superheating twice, and not only entirely suppressing the cylinder condensation, which still remains
to the extent of 20 per cent even in that form of engine,
but also of adding about one-sixth to the work of the small,
and one-third to the work of the large, cylinder, or say
25 per cent to the work done by both, making a gain of
about 42 per cent in power produced, to accomplish which
the expense of superheating would be about 18 per cent.
This is on  the  supposition that 400~ in  the cylinder
is our limit.  If it should prove that superheating can
safely be carried to 5000 in the cylinder, as it appears to have
been in the " Georgeanna" experiments, or even to 470~, a
still farther economy of 10 per cent purchased with three
per cent of fuel will be practicable.
SECOND  METHOD OF SUPPRESSING CYLINDER
CONDENSATION.
Although I have not thus far stated it in so many words, it
will no doubt have struck you, that a totally distinct method
of suppressing cylinder condensation grew out of the investigation made to determine whether the refrigeration taking
place in the cylinder was the equivalent of the whole work
done, or only the equivalent of that done after the cut-off;
and it will be seen that this distinct method consists in the
use of superheated steam regulated at each cut-off, so as not
to exceed a safe temperature in the cylinder:'and it will be'Thisi:tlvan:t:ag of 20 per cent can b!e,:ined without exceeding the
temlper:ture of saturatedl steam of the pressure usel; experience will
show what fiarther gail can be seclured without inconvenience.
*    See nlotle pave 3.5.




46
seen that by this method we not only suppress cylinder condensation, but gain other very considerable advantages growing out of the increase in the bulk of the steam, by reason
of the heat added to it, over and above the temperature of
saturation.
REVIEW.
Let us now review briefly the ground over which we have
gone.
We have seen that cylinder condensation causes an immense loss in the working of steam engines, varying from
20 per cent (of the steam  utilized) in the best jacketed
compound engines to 142 per cent (of the steam  utilized)
in  good, tight, single  cylinder engines, well protected
by lagging, but using saturated  steam; that is to  say,
whoever is now  using steam  may save from  one-fifth to
one-half of his coal bill by simply suppressing cylinder condensation, and may save a still further percentage by a judicious application of the principle of superheating. We have
seen that the primary causes of cylinder condensation are
external radiation; conversion of heat into work; internal
radiation; and conversion of heat into the work done during
the first rush of the steam from the cylinder after the opening of the exhaust; and that these four causes are diminished to a slight extent by the superheating growing out of
the expansion of the steam per se.
We have seen, moreover, that the total effect of these primary causes amounts to only a small fraction of the actual
condensation observed; say to about 16 per cent out of the
142 per cent.(of the steam utilized), which was seen to be lost
in the last experiment of the " Michigan."
Furthermore, we see that these primary causes can only
act to such an extent as they are able to chill the internal
metallic surfaces which are present and acting at the point
of cut-off. These alone affect the quantity of condensation;
the rest of the cylinder only acting to affect the working of
the steam after the cut-off.
We see that the internal metallic surfaces present at the




47
point of cut-off must, when the engine has-attained a regular
action, receive at each stroke from the incoming steam an
amount of heat precisely equivalent to the amount of heat
lost by them through re-evaporation, plus the amount of heat
lost by them through the action of the above mentioned primary causes. For if this were not the case at any particular
stroke, the surfaces in question would be found upon the
next stroke either hotter or colder than they were before, and
a smaller or greater proportion of the incoming steam would
be condensed until the equilibrium was established.
We have seen, furthermore, that the internal metallic surfaces present up to the cut-off multiply by cumulative action
the effect produced upon them by the above-named primary
causes, and that the coefficient by which the effect of these
last is multiplied is equal to the amount of steam condensed
by the surfaces divided by the amount which fails to be reevaporated,
I have not then Presented to you simply a mass of experiments seeming to show that cylinder condensation is very
important, without accounting for it; nor have I endeavored
to persuade you of its importance from theoretical considerations unsupported by experiments, but I have exhibited to
you the experiments which establish the facts, and have explained how theoretically these facts can be accounted for.
This being done, I think the phenomena may be accepted
without reservation, and that whoever uses steam may rely
upon it that he may, if he chooses, save from onefifth to onehalf of the money which he expends for coal.
Two methods of doing this have been described to you.
First, that of keeping the cylinder at a heat regulated at that
point at which its internal surfaces will repel the spray formed
by the conversion of heat into work; second, that of superheating the steam to the degree proper for each different cutoff in such a manner as to supply the heat converted into
work and to furthermore superheat to such a point as shall
be without danger to the internal metallic surfaces.
Singularly enough, both of these methods have been, in a




48
hap-hazard manner, verified by experiments, the record of
which have been many years before the public.
The first method was verified by the experiments of Sir
Daniel Gooch upon locomotive engines made in 1849 and
1850, but rejected up to the present day because they could
not be accounted for, or, in other words, found to be in accordance with other known facts. They are rejected entirely by
"Engineering" in an article upon " Urban Railways," dated
March 13, 1874, and in a leader of March 20, 1874, because
it finds that the surfaces of the cylinder were very much
smaller than the superheating surfaces used for the very
moderate amount of superheating now practiced in marine
engines..
But when we consider that the work to be done by the
cylindrical surfaces was not the re-evaporation of all the
spray caused by the conversion of heat into work, &c., but
simply such small portion as could be re-evaporated during
the short period occupied in the stroke, and this by radiation
and not by contact, the objection drawn from the practice of
superheating seems altogether to fail, and the experiments
remain unshaken.  Any engineer, who will calculate the
amount of work which can be obtained from steam of a hundred pounds pressure, expanded four-fold and very slightly
superheated, will find no difficulty in crediting the results
described, which were nearly equal to those obtained by
many compound engines.
The second method has been verified by the " Georgeanna"
experiments, the results of which one would have thought
sufficiently extraordinary to awaken an enduring interest.
They certainly did attract much attention for a time, but
failed to produce a permanent effect; first, because if superheating be not carried to the point necessary to supply the
heat converted into work, and the amount abstracted by radiation, it fails to suppress condensation, and the result does
not repay the trouble and expense which has been incurred.
For instance, in the experiments made by Mr. Isherwood, with
superheated steam, upon the steamer "Eutaw," subsequent




49
to those made upon the " Georgeanna," the best result obtained was at a cut-off of 29 per cent, and with the steam
superheated to the temperature of 396~, when a total horse
power cost 28.4 pounds of'water evaporated per hour; and a
consumption of 3.4 pounds of coal, whereas with the " Georgeanna" cutting off at 28 per cent, the total horse power was
obtained by the evaporation of 16.4 pounds of water per hour,
and the consumption of 2.2 pounds of coal. This last was the
experiment E, shown in the table of the " Georgeanna " experiments, in which the probable temperature of the steam in the
steam-pipe is shown to have been 452~. Here, then, we'see
an enormous difference, caused by a difference of only 56~ in
the amount of superheating; but I think what we have said
before will enable us to account for this somewhat perplexing
result. The superheating used in the "Eutaw" appears to
have been sufficient to counterbalance two-thirds of the refrigerating effects produced by the conversion of heat into
work, and by radiation. But, on the other hand, the internal
metallic surfaces having less to evaporate, would doubtless
evaporate a larger proportion of the water condensed at each
stroke, and so increase the coefficient by which their accumulative action would multiply the remaining effect of the
primary refrigerating causes. We thus see why, in the
"Eutaw," a superheating of 127~ reduced the cost of the
tdtal horse power only from 32.75 pounds of water to 28.4
pounds of water, and the cost in coal only from 4 pounds to
3.4 pounds; whereas, a further superheating of 51~ in the
" Georgeanna," brought down the water evaporated per total
horse power, as already stated, to 16.4 pounds, and the coal to
2.2 pounds.
This shows, that if we would, at a short cut-off, obtain the
advantages due to superheating, we must raise the temperature of the steam to that point which will absolutely suppress
cylinder condensation; and I have shown that if we wish to
obtain all the advantages derivable from the use of this agent,
we must raise the temperature still farther, until about 400~
F. of heat are maintained in the cylinder. But I have also




o5
shown that the superheating necessary to produce this effect
at short cut-off would be too great to be used with a longer
cut-off, as the engine would be damaged thereby; and this
leads us to the second reason why superheated steam may
have come so little into use. Many engines have been injured
by it, engineers not being aware of the fact, above stated,
that the degree of superheating must be properly regulated
for eaoh particular cut-off. Now, however, that this fact is
demonstrated, and an indicator provided, there remains no
obstacle to the use of the great economizer, and it will be
seen that I stopped far short of a full statement when I said
that whoever now uses steam may save, if he chooses, from
one fifth to one half of the coal he is consuming.
The facts, and their explanation, as laid before you in this
paper, are briefly stated in the patents which have been granted
me at Washington, and have neither been contradicted nor
questioned by the examiners at the patent office.




51
TABLE I.
EXPERIMENTS ON THE STEAMER "MICHIGAN" AT ERIE, JANUARY, 1861.
1.      2.        3...      6.        7.       8.      9.      10.
4-9 47.  "        3.      3.261    2.350.911   38.8 ^"    2.4.887-  5.8  "
0U                                                                            - i3~0    4  B~E
"             33.0    3.261      2.350.91 1   38.8     2.37.887
3-10  33.8  "    33.4    2.865     1.696   1.169   68.9  "   1.671   1.194   8.4  "
1-   29.1 "      33.3    2.53      1.453.000   68.8  "    1.481.972   9.   "
1-6   21.2  "    33.2    2.060     1.056   1.004   95.1  "    1.192.868  11.5 
4-45  13.9 "    33.0    1.659.686.973  141.8 ".910.749  15.5* "
* This strictly ought to have been the amount used on pages 16, 17, and 18, instead of 12.5
per cent, which, however, is the percentage of condensation due to the conversion of heat
into work, after allowing for the greater heat contained in the steam at cut-off over that at
the end of the stroke,
y*    *   3*1~~~~~,  CmsQ                        z;)H  E-a                   c
the end of the stroke.




TABLE  II.
EXPERIMENTS ON THE STEAMER "GEORGEANNA" IN CHESAPEIKE BAY WITH SUPERHEATED STEAM,-MADE IN 1862-63
CALCULATED  ON THE SUPPOSITION THAT CALCULATED ON TIIE SUPPOSITION THAT
THE THERMAL EQUIVALENT OF THE                  THE THERMAL EQUIVALENT OF THE POWWHOLE POWER  DEVELOPED  IS TAKEN   ER DEVELOPED AFTER THE CUT-OFF IS
FROM THE STEAM IN THE CYLINDER.                TAKEN FROM STEAM IN THE CYLINDER.
EXPERIMENT.                             A.   B.    C.   D.   E.    F.   G.             A.   B.   C.    D.   E.   F            G.
1.  Actual Cut-off, per cent............................    47    66    47    66    31    47    66  47    66    47    66    31    47    66
2.  Heat converted into work measured by steam......   266'  243~  301~  289~  328'  307~  288~    125~   78~  138~   88~  188~  134~   89
3.  Deduct greater heat in high-pressure steam at Cutoff over that at the end of the stroke measured as
steam............................................      25    15~   25~   16~   42'   27~   15~         25~   15~   25~   16~   42~   27~   15~
4.  Difference between last two lines....241   228.  27    273   286'  280 "41   228   2  273   286    80   273  100'   63   113'   72   146   107    74
6.  Calculated temperature of the steam in the cylinder at cut-off...............................    263~  332'  353'  501i  274'  396'  489~    263~  332~  353~  501i  274~  396~  489~ 
6.  Sum of last two line........................504   560   629   774   560   676~  762'    363   395   466   573   420   503   563
7.  Same as line 4.......................................    241   228~  276~  273*  286~  280~  273~    100'   63~  113~   72~  146~  107~  74
8.  Calculated temperature of the steam in the cylinder
at the end of the stroke..............    247~ 331~  358~  433~  256~  348~  438~    247~  331'  358~  433~  256~  348~  438~
9.  Sum of last two lines................................    488~  559   634'  706~  542~  628~  711~    347~  394   471   505   402'  455   516~
10.  Temperature of steam in steam pipe necessary to
furnish the heat converted into power; 50~ added
to last line for radiation...........................    538~  609~  684'  756~  592~  678~  761~    397~  444~  521~  555~  452~  505~  566~
11.  Temperature of mixed steam  shown by thermometer, but undoubtedly inaccurate.........................  344   338   336   336   322~....  344~  338~  336~  336~  322~
12.  Line 11 plus 60~....................................   404~. 398~  396~  396~  382~......  404~  398~  396"  396~  382'
13.  Temperature of superheated steam  shown by thermometer, but undoubtedly inaccurate................           530~  544~  474~  534   498.......  530   544   474~  534~  498~
14.  Line 13 plus 75.................................                    6 605~   619~  549~  609~  573~........  605~  619~  549~  609~  573~
NOTE. -Experiments A  and B were made with the steam  chimney alone without the superheater. In Experiments A and E there was a slight
condensation, and the heat necessary for its re-evaporation %oAuld be addeld to Ilo 10.  1-cx       x-e- ^-~ff-7l/ -t-oL-v         _ - cyQ L




53
TABLE III.
SUPPLEMENT  TO  TABLE  II., EXPLAINING  LINES 5 AND  8.
1.    2.      3.        4.        5.       6.       7.        8.       9.      10.
4 K <   4 3
8  br   H            ~4      s:sa   i;<NH, v
A.  45 per et47 per ct804,000   782,000   263~      263~     832,000   223~    247~
^  ~.m 9,10.
E.  28 " 31 "         920,000   917,000   274~     274~     983,000   210~     26 
0r-           P0:~                            00
F.  45 "   47 "        623,000   738,000   262~    396~      741,000   219~    348~.  65 "   66 "         60,000   803,000   255             51~ 9787,000   227~    438
~  I                                                   c
A. 45per      e  te peratures   of  the          superheated           steam  in the247
B.  65" 1 66" 11  823,000   914,000   253~          3320    942,000  -5320    3320
cylinder. 45  7        943,000  1,061,000   263     353ere calculated  from  the358
1).  65 "   66 "       708,000   952,000   255~    501~    918,000   2290    434~
E.  28 "   31 "6    920,000   917,000   274~    2740    983,000   2100    256~
F.  45 "   47 " 1   623,000   738,000   262~,   3960    741,000   219~    3480
G.  65 "   66 "        602,000   803,000   251~    489~    787,000   227~    4380
The  above  temperatures of the  superheated  steam  in the
cylinder, given in columns 7 and 10, were calculated from the
following proportion:
The absolute temperature of saturated steam at the given
pressure: the  absolute  temperature   of  the   superheated
steam, to be found = the volume of saturated steam at the
given   pressure:  the   actual  volume   of  the   superheated
steam.  The latter ratio = the volume of saturated steam at
the given pressure X  the weight of one cubic foot of that
steam: the volume of the superheated steam X the same
weight of one cubic foot of saturated steam; or what is the
same thing, =  the actual weight of the superheated steam
used: the weight of that steam supposing it to be saturated.




54
Then, for instance,
Column 4: column 5 = column 6 + 461~: column 7 +
461~; and in the case of experiment G.,'we should have
602,000: 8030000 - 251~ + 461~: absolute temperature of
the superheated steam at cut-off =  712~: 950~.  950~0
461~ - 489~, as given in column 7.